Why does my car start but stalls when I stop ONLY WHEN RAINING?

Could be the C305. Lots off problems with that design. Water gets in, messes with the electrical, check engine light comes on, and start problems occur. I'd check the connector for corrosion. You're lucky that you only have problems when it rains. I carry electrical cleaner in my purse (because it can explode in a hot car) in case it stops working. You can do what's called a c305 ectomy, but I'm not willing to mess with all that myself. Hope this helps!