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Here in central Florida, the only reason we don't hit 100% humidity is because the mosquitoes are taking up too much space that water molecules might otherwise occupy.
Another explanation not mentioned here, about why skin feels dry on a cold, humid day, is 𝙩𝙝𝙖𝙩 air gets warmer next to the skin or by the building we're in, so it's now relatively dry. That's why indoor humidifiers are handy in cold seasons. Precipitation happens for the opposite reason. It can be analogous to a soaked sponge which is squeezed when it's cold and released when it's warm.
The one thing you’ve got to consider in the winter is that, unless your walls use thermos technology, there’s always air exchange between the inside of the walls and the outside. What that ends up meaning is that if you humidify the air *too* much, then when that air gets inside the exterior walls and perfuses through the insulation, it will still be full of that humidity when it comes into contact with the much, MUCH colder outer side of the exterior walls. This can unfortunately tend to cause water to condense and build up inside the walls, leading to water damage, rot, and mold. You might’ve seen an extension of this effect if you’ve ever had an absurdly, like -10 to -15°F or lower, cold morning where you live and woken up to find your multi-pane, usually draftless windows partially coated with a layer of frost on the inside.
@@MegaBrokenstar And that is a key to the use of vapor barriers. In climates that get cold, it is important to use a vapor barrier on the INSIDE of the insulation (not breathable 'house wrap'). This helps prevent the humid air inside finding it's way through that insulation and doing just as you said. But in muggy climates (think Gulf Coast of US in july), the opposite happens and you the same problem in reverse.
Well, your hair IS essentially a hygrometer! ^_^ A lot of the old ones work exactly like that: there is a hair in the meter and depending on the humidity in the water, it expands or tigthens on a coil - which you can read as a measurement and if calibrated correctly gives you an old-school hygrometer...
Titaniumjackal not really clickbait. Look around and the world is full of people who don't understand some basic science. I knew what the video was going to get at and I still enjoyed the explanation.
In 1939, actor Peter Lorre played the lead in a movie titled _Mr. Moto on Danger Island._ At the end of the picture, an actor named Warren Hymer spoke the line, “It’s not the heat, it’s the humidity.” People have been saying it ever since.
It is literally true though. Really low humidity and I was fine on a long walk in 105 F. But I have sweat my guts out with moderate humidity in the 80s.
Due point is commonly reported lots of places. Also, the humidity measures you see in a weather report are typically derived from the difference between wet-bulb and dry-bulb temperatures. That's the old fashioned and in most ways still best way of doing it. So... This video is the rare fail from SciShow IMO. PS: That said, digital RH sensors are super convenient. SHT31 is my favorite.
Try in north Dakota. It gets almost as humid as houston in some places (not as hot most of the time, though!) And I'm the winter we regularly see temperatures in the double digits below 0. The apparent humidity is WILD
@@LawTaranis Houston is a dry heat Alabama is a wet heat wanna trade, well I think about that either, about that It does snow some here when I was growing up it dumped a load of snow in May, yeah but it hasn't done a repeat
If you like another method of findingout what the temperature "feels" like, Humidex is used in Canada quite frequently. Similar to wind chill, it uses the temperature and relative humidity to state what the temperature "feels like" to a regular person. It might be only 31°C, but it will feel like 38° with 55% humidity. It takes into account the fact that the air cannot pull your sweat off. Wind chill is the same, but uses wind speed and temperature instead, and is used for cold weather
I’m familiar with wind chill and heat index, but I know they have their limits. I have tried calculating heat index and wind chill and I get things like humidity lowering temperature and wind raising temperature, which happens in the real world every year, but breaks the limits of heat index and wind chill. One calculation I’ve done is wind chill for 80 degrees F and 60 mph winds and according to that, I get 82 degrees, an even warmer temperature. On the one hand, wind warming temperatures happens all the time. On the other hand, I’ve been in conditions close to that calculation and in my experience, 60 mph winds always give a chill regardless of whether it’s winter or summer weather. So, it would be nice if the meteorologists here in the USA extended the wind chill from a maximum of according to some sources 50 degrees F and according to other sources 70 degrees F to summer temperatures.
As a teen, I had an amateur weather station that I used to make my own weather reports. It included a pair of thermometers, one normal, one with a gauze "string" attached. This one was to be kept wet so that the difference in wet temp could be measured. Through the dual readings and a bit of simple math, the humidity could be determined. It wasn't rocket science, but it worked.
That is called a "wet bulb" temperature. It measures how much cooling you can get by evaporating water into the air. The wet bulb temperature is always between the dew point temperature and the "normal" air temperature. That is, it is impossible to cool air all the way down to the dew point temperature. Thiis also has a direct effect on how effective a "swamp cooler" is. In places with a high humidity, and therefore a high wet bulb temperature, evaporative cooling systems don't work.
I'd say the actual catch is that our body temperature (and, oftenx the temperature indoors) is mostly fixed, which makes the relative humidity of those places significantly lower than that of the environment if there's a big temperature gradient
THANK YOU! Humidity percentages have confused me often... I had already learned about how it's relative to the amount of water the air can hold, but I didn't think about how that would change at different temperatures. Finally, an explanation for the lack of consistency between a percentage number and how humid/dry it feels...
I don't know how many times I've explained this concept after learning it in one of my atmospheric science classes. My mind was blown when I finally understood this.
Dew point measurements are hardly new. All you need is a wet bulb thermometer, much less complicated than a hygrometer. It's just a regular old thermometer with a cotton wrap on the bulb that gets water put on it.
It is called a sling-thermometer. It is a thermometer in a cotton sling. You wet the sling then spin it around to achieve maximum evaporation to get an accurate reading.
@@samarnadra High heat, low humidity. Everything dries out immediately. Higher heat = more potential water in the air, yet we have only 13% on good days, until monsoon. Jerky is easy to make though, just cut season hang and it's guaranteed to dry out fast.
Thank you for including Fahrenheit references, makes it much easier for those of us who weren't blessed enough to grow up in a metric country. wish Sci Sho would do this with all of their vids.
I am born and raised in Calgary Canada, border line desert, it frequently gets to around -30°c in the winter, and when there is higher "humidity" at that temp it just means that there is going to be ice crystals floating around (yay sundogs!) but it's definitely still "dry". Not sure how relevant that is, but hey, gimme a soapbox and I will proclaim! Love the vids guys!
I bought a humidifier this winter and OMG I don't understand how insanely good it is. no dry mouth no itchy skin no chapped lips or dry skin. get one you will love it!
@@kellyrowland9470 - That's exactly the kind of humidity we have here year long (I just confirmed: hygrometers are of little use when they always read "high"). Nobody grows mushrooms that I know of however.
@@madamsloth it's part of a big clock that was left in the house we bought a few years ago. Giant atomic wall clock with a thermometer and hygrometer. It's freaking awesome!
I have one, too in my bedroom. Mine has temperature and humidity. In the winter I run the humidifier. In the summer, the dehumidifier. The hygrometer helps me to know I'm not insane when it feels time to adjust the humidity.
Mine is no help: it always reads "high" and does nothing at all but sitting there all the year without giving any info or doing anything. Seriously: I've seen hygrometers since kid and always have the suspicion they are all broken because the needle doesn't even move (but then they never say "low", which would contradict the facts, so maybe they are working perfectly).
One of the other useful things about dewpoint is that it often tells you how low the temperature is going to get at night. This is because as the temperature drops, each degree of temperature drop takes about the same amount of energy loss. This all all changes though when you hit the dew point and to get lower, the dew point has be lowered by condensing water out of the air. This takes a lot more energy. This is pretty clear if you look at the daily temperature graph in a humid area. The graph looks really flat at the bottom where the temperature hits the dew point.
I was a crew chef on a helicopter. On some morning if you were the first in the air that day and it was really close to the dew point. You could look behind the aircraft and see the fog forming where we had just been. Was awesome
Well, since this video was disappointing, I will share something I only wrapped my brain around recently. Relative humidity is the ratio between the current partial pressure of gaseous water and the vapour pressure of water at that temperature. It really has nothing to do with the air, other than its temperature, and the air doesn’t really “hold” water. Partial pressure is like this: If I have a gas mixture of 80% nitrogen and 20% oxygen, and the pressure of that gas is 1 bar, then partial pressure of the nitrogen is 0.8 bar, and the partial pressure of the oxygen is 0.2 bar. Vapour pressure is like this: I take a gas bottle and pump everything out of it so it is a complete vacuum, then I add some water to it. Some of the water will stay as a liquid, and some will turn into a gas. The pressure of the gas at a given temperature is the vapour pressure. If I heat up the gas bottle, the liquid water will boil, the vapour pressure will increase and there will be more water as gas and less water as liquid. (this is how heat pipes work btw) The vapour pressure of water is pretty low, 23.388 millibar at 20C. If the partial pressure of the water vapour in 20C air was 23.388 mbar, the humidity would be 100%. If the partial pressure of the water vapour in 20C air was 11.694 mbar, the humidity would be 50%. As usual, if I’m wrong, the internet will correct me shortly.
% RH is something that I have understood for so long that I don't ever remember not understanding it. But I am probably getting old, and measuring environmental conditions is part of my occupation. Learning that the measurement confuses people that don't need it in everyday life is like when I had the epiphany that a friend didn't understand how variables were used in algebra. I was trying to help them with their homework, and they kept nodding, but didn't actually seem to get it when completing assignments. Once I understood that "letters in an equation" didn't make any sense to them, I was able to properly teach! Always ask questions! We all have different life experiences and are operating from our own, accumulated data sets. Sometimes, things that seem simple and universally understood to one person are alien to another, but we all are capable of understanding if we have the time and the want to.
I always thought that relative humidity was a measure of how angry our mom got at us kids. She could get really steamed up with us. Looking back I can't say I blame her! lol
@@LuinTathren I would like to thank my mother and my brothers and sister without whom this award would not have been possible. I shall honour it and it is as much for them as it is for me. Thank you to all who voted Thank you and I love you all!
Was only this weekend wondering about this. Temp/RH monitor in green house rigged up recently. Temp goes down over night and HR goes up and vice versa in day. Makes sense now!
"Relative Humidity Isn't What You Think It Is" No, apparently it's exactly what I thought it was. This is common knowledge. Relative humidity is simple-if you know the definition of the term, you know how it works. It's great that you are teaching that definition to people. And the addition about the dew point temperature is helpful. But I hate these clickbaity, patronizing titles that assume the viewer is ignorant. Maybe it's just a pet peeve of mine, but I find it SO off-putting when I see articles and videos with titles like, "Five Things You Didn't Know About [X]." This isn't Buzzfeed. SciShow is above that. You could just as easily use "Why Relative Humidity Can Be So Confusing" or "How to Understand Relative Humidity" or better yet, include something about how you are actually comparing it to dew point temperature. IDK, maybe I'm just too uptight, but I just feel like SciShow has some of the most passionate viewers of any edutainment platform. Why condescend to them?
Did you learned something from the video? Maybe it's just not for you. I didn't actually knew the definition of relative humidity; and barely ever heard of "dew point", to the point that I don't even know what's the term in my mother tongue (and I'm just going into a little internet search to find out...)
@@the-mush There are 5 or 6 other top comments with the same premise as mine. There's nothing wrong with this video. My problem is chiefly with the title. There are plenty of SciShow videos that teach things I already know. That's just how education works. I'm saying that the title is what is condescending and doesn't match the subject matter of the video.
I think the premises are wrong. Relative humidity is exactly what your body feels since it correlates to the evaporation rate in your skin. So 70% in the summer OR winter is the same. However if it's 70% outside un the winter, when the air comes inside it drops to, say, 30% which is very little
So, relative humidity is exactly what I think it is... So now I'm being dissed for actually remembering the definitions that have been common knowledge for a long time.
Air doesn't really "hold" humidity if there were no air the water would still try to evaporate till there's an atmosphere of water vapor at the vapor pressure for that temperature. And relative humidity is the percentage of vapor pressure that the current partial pressure of water vapor is.
People plan their day with humidity? We don't even look at it. All we know is that if water starts condensing on random walls, the humidity just went past 100% again.
Yeah, I’m not really sure how it would factor into planning the day, other than putting extra serum on your hair, maybe. But it’s usually very humid here, so I guess we just always expect high humidity.
If the relative humidity is in the 90s at night, that still means that the sweat on my skin can't evaporate because there's already so much water in the air. The total amount of actual water in the air may not be any more than in the day, but if the air can't hold as much water at night, the sweat has nowhere to go. I live in Florida without AC, and the humidity gets unbearable at night.
Can't really understand why dew point should represent humidity better. If we take a closed enviroment and raise the temperature the air will feel drier, the dew point stayed the same only relative umidity changed (preassure should not change). This example can be observed during winter if you turn on the heater and you do not have a humidifier. Sorry for the bad english
@@DaimyoD0 Does make sense! Just was a little disappointing to realize I already knew a lot about the topic. Did learn what the "dew point" is called though! So I did still get to learn something. I knew the concept, but not the name.
I think you forgot an important part of your explanation. The Dewpoint is the temperature at which air, with as much moisture in it, as there is in the air right now, would condense into dew. If the air today has very little moisture in it, it would have to get pretty cold, before it would be so saturated that it would condense. If the air has lots of moisture, it has enough to condense at a much higher temp.
Dhahran, Saudi Arabia once had a dew point of 35 °C (95 °F) with a temperature of 42 °C (108 °F) in July 2003. This made it “feel” like 174° (79°C) 😳 imagine that!
I learned about dewpoints years ago when I took pilot training. Today, at home when I need to decide whether to open the window for cooling, or use the air conditioner, I check the weather report and see if the dewpoint will be below or above 55ºF (as well as the outside temperature being appropriate). If the dewpoint is below 55ºF, I know that when that outside air comes in and warms up to room temperature, it will be a comfortable humidity level.
I thought relative humidity is important not for the "feeling of stickiness" but for how much it adds to the feeling of heat, because relative humidity affects the rate of evaporation of sweat off your body more than absolute humidity.
You should do one of these for the Sun Protection Factor (SPF), the one in sunscreens. It's commonly confused with a percentage (%) of protection against sun radiation. But it actually isn't
It's also worth noting that the relative humidity will be extremly low indoors when the temperature outside is low. If it's - 15°C outside with a humidity of 90% and you take that air inside and warm it up ro 20°C that humidity will drop like a stone contributing to the dryness of the indoor air in winter, and the colder it is outside the more pronounced the effect is.
Former floridian, the relative humidity has always been high and always made you feel drenched in sweat after five minutes of being outdoors. Compare that to living 5000 miles+ upwards in Colorado, 5 minutes with the same relative humidity, i don't feel hot and sticky.
Another common misconception is that when the relative humidity gets >=100%, it will start raining. Not necessarily. The default when the relative humidity reaches 100% is the formation of clouds, ie fog when it happens at ground level. More than just that has to happen for rain to form.
Also, fun fact, there is wet bulb vs dry bulb temperature, which is an even more effective method of measuring comfort. Wet bulb temperature indicates how effective evaporative cooling is when you are in a ventilated area with consistent dry bulb temperature. Dew point can be used to approximate the wet bulb value, but is not as accurate, due to the nature of predicted vs measured values.
I always thought relative humidity implicated how much the air absorbs water molecules from surfaces (like you know, your skin). High relative humidity (i.e. inside a cloud) already feels kinda wet, so it wouldn't absorb any more moisture from you. The opposite from a dry air. But indeed the "feeling" of relative humidity kinda feels logarithmic with temperature. Or exponential, depending on how you frame it (by "feeling of dryness" or "feeling of moistness").
I've heard if the humidity is over 50% you can ball park the dew point by subtracting the humidity (as a whole number) from 100 and divide that result by 5, that will give you the degrees, in Celsius to subtract from the temperature to get the dew point. (75 F and 60% relative humidity = 60.6 F ( 100 - 60 = 40, 40 / 5 = 8, 8 * 1.8 = 14.4, 75 - 14.4 = 60.6 (actual dew point would be about 62F)
This is also how dehumidifiers & Air Conditioners work: by cooling the air below the dew point, a lot of the water vapor condenses & they blow out drier (& cooler) air.
"Water must go from a gas to a liquid"? Does not sublimination work both ways? (You can dry your cloths in sub-zero C° degrees, due to waters ability to subliminate).
Fairly certain it is exactly what I think it is. It is the ratio above or below the point where evaporation balances out condensation. With 100% being perfect balance and 0% being no condensation.
What?!? Who doesn't know that you're not going to be sweaty in the cold? Relative humidity tells you things like how quickly (if at all) things are likely to dry... when the number goes up, things happen like wood starts to expand, superglue will set quicker, all kindsa things, why would you want to know "the temperature when things would be different if it were that temperature"?
*SO comes into kitchen in the morning* Me: You should go outside, it's muggy out today Them: I swear to God, if all our mugs are out on the front lawn... Me: *Smugly sips coffee from a bowl*
Of course it might have been useful to note the point of difference between Temp and Dew Point where the humidity has its most obvious effects, as in when it will 1) Fog Eye Glasses 2) Fog The Air 3) Produce Drizzle
Just for fun I paused the video and checked the dewpoint here in Tucson, AZ. It was hilariously low at 21°F (-8°C), with an air temperature of 81°F (27°C) . . . ah, life in the desert! 😎
I now find dew point to be more useful to know if the day will feel humid or not. With relative humidity, I don't always know if the percentage for each degree is a lot. It's too damn relative. With dew point, 15-21 is in the danger zone to keep in mind, and then the hotter the day gets, the shittier that humidity gets. That's a lot simpler from what I'm picking up.
So yeah, the problem with relative humidity is that (1) we tend to assume that percentage scales are defined by _immutable_ reference points, when (2) in this case the reference point (i.e. 100% RH) is highly _variable_ because of its correlation with temperature.
Well that explains why I've felt terrible all day! My sinuses like to throw a fit when it's dry but it's hard to tell if it's pure allergies or allergies that have been exacerbated or pure dryness. Turns out it's very dry today! We're at the point in the year where relative humidity isn't particularly intuitive because it's still pretty chilly, but the dew point is only 23F
Fun fact, most early hygrometers used hair, often human hair, to measure humidity. Imagine putting a pen on a drum of paper and spinning the drum. Then tie the pen to a long lock of hair on one side and a spring on the other. As the hair started to shrink it'd draw the pen towards one side, thus creating a real-time humidity graph.
A few weeks ago I put a thermostat/hydrometer in front of the vent on my window AC, I assumed the air would be bone dry and cold, it was cold, but showed a humidity level of 80-99%%, I checked another meter further in the room, and it showed about 60% humidity. That was when I, unintentionally, finally grasped the concept of "how much water the air can hold at that temperature" I was messing about because I bought about a dozen of the meters for cheap off Amazon because I wanted to see if I actually needed a dehumidifier in my room/house (Mississippi), I do :/
2:08 things get unpleasant around 21°c & here where is at 42°c with 75% humidity unlike desert country where humidity is like around 15% so it's ok, but 75% even with 42° 🥵🥵🥵
One tv station's local news would report the dew point and I LOVED them for that. "Humidity is 65% today..." doesn't tell me anything. But "and the dewpoint is 45 degrees (Fahrenheit)" tells me it's going to be a pleasant day. :)
I knew an engineer that believed air-conditioning increased humidity. He based that on when he came home he would check his humidistat. When he turned on the A/C. The reading increased as the temperature dropped. He was an electrical engineer. He couldn't quite grasp the relativity of the psychronometric chart.
Very interesting looking at my hot house data logs in the afternoon's. One temperature I never want to feel again is 70c and 100%Rh. The feels like temperature is over 155c!
I used to live in southern Louisiana and I can tell you that when it’s 99 degrees out and the the relative humidity is also 99% that air can hold a LOT of moisture. Contrastingly, I currently live in New Mexico where relative humidity normally sits below 20% and has been known to be in the single digits fairly often. When the air is cool and can hold very little moisture and the relative humidity is like 8% of almost nothing in the first place... that’s pretty much the definition of “bone dry” as they say.
It sucks to have extremely low humidity at high heat because the air WANTS to be wet. Bone dry is 4% at 105* F like in arizona. The water WILL leave your body.
@@D-Vinko well 100+ degree air at 4% is about 40g/kg of water/air whereas 8% at say 60 degrees is about 6g/kg... and even 20% at 30 degrees is about 0.4g/kg according the website Engineering Toolbox. So yeah the summer sucks and the heat is terrible... the most drying climate is one in which its dry during the winter. That’s when your skin starts to crack on your hands, you wake up at night absolutely parched, your lips are constantly chapped, your eyes feel like needles are being inserted at the slightest breath of wind, you get nosebleeds regularly... cold and dry isn’t as immediately uncomfortable as 100 degree temps, but it’s very taxing on the long term.
Man, I really wish you put this video out two weeks ago, because I just bought a little thermometer/relative humidity device and I was wondering what exactly those numbers mean. Now I know they mean nothing usable
Relative humidity is easier to understand, but dewpoint is a more accurate descriptive indicator. I prefer RH. I'll know if it's hot _and_ humid _or_ cold _and_ dry with two numbers. No calculation required.
It gets more confusing if you want to estimate if that relative humidity will dry a solid, like grain, that isn't necessary the same temperature. The solid has in a different relative humidity in effect.
The highest summer humidity in the world can be found in the eastern coasts of Arabian Peninsula. August here is chocking. I like humidity but here it's too much. The humidity I like is in tropical wet climates not here in the desert.
