I live in the foothills above the Great central valley of Kalifornia. The valley is technically a desert, ie, ~10" of rain/yr. I may get 20-40" per year in the hills. Low temp is ~15° (once every 10 years). Snow comes ~4" every 5 yrs or so. We have no winter here, to speak of. I believe we do pretty well in the summer dept. though. So in winter, I like having what rain might come just roll off the shade. Though after a full winter with my shade, I never remembered that value (that is a function of the amount of beer I drink) but, felt SO COOL tooling around in the rain and not getting a direct hit from it. I like watching it just drip off the edges and laugh ... I am single and insane so your milage may vary /forums/images/graemlins/crazy.gif
Check out a search on TBN for those who have bought the ~$100 golf cart rain cover from NorthernTool. It's supposed to fit right over a shade and provide a nice cheap winter "cab".
Cheers!