Ugh...humidity! It's something you NEVER get used to!
Something to keep in mind...If you're sweating a lot, you need more water. If you don't drink enough water, your body's going to hang on to every last drop, which will show up as a weight gain. Try to drink a gallon of water today (that's about a half-cup shy of four liters). It sounds like a lot, but it will help your body's water regulators get back on track.
Jennelle