I find this post very interesting, as I have just the opposite experience. My RSI symptoms are aggravated by cold. I am always trying to keep my hands and arms warm. Warm and dry are the best conditions for me.
So, in the winter, I wear long sleeves, and sometimes wrist bands, or fingerless gloves. In the summer, I just try to combat the (unnecessarily cold) air conditioning by stretching and taking the occasional walk into the shop or outdoors.
Oh, there's another thing I do to deal with the moisture in the summertime. I have a small Altoid's tin at my desk with Dr. Scholl's foot powder in it. I'll dip my fingertips into the powder to dry them, and make them slide better over the TouchStream.