THANK YOU SO MUCH. I recently switched to my first ever Android phone, the S5, and I deleted the weather widget but now I want it back. Still figuring out this phone, was very frustrated trying to figure out how to get to my widgets. So thanks.
On top of that, you can also access the hidden widgets button by two other ways (in case your home screen is full of apps or widgets) by 1) "zooming out" or pinching the screen or 2) press and holding the Menu Key in the lower left corner (must press and hold or you'll get the "Repeat" key).