I have never seen flays in the rain. where flies go when it's raining?
I used to work outside in the MidWest and it would often rain during the late summer months. I worked in a tent selling produce, which (of course) attracted a lot of insects. Whenever it would rain we would suddenly have a ton of flies sitting on the counter or walking around on the plants we sold on the side. I have the feeling that, in nature, when it rains, the flies do what the rest of us do......they hide.
I did some searching, but did not come up with a convincing answer. The "best" answers I saw were from Yahoo! Answers, which I try not to cite unless they themselves cite a source.
The general opinion was that flies do hide, as mercutiom says. That does sound reasonable. It also seems that they can avoid raindrops -- or that the raindrops exert a pressure wave that diverts them aside. But since I too haven't seen flies in the rain, I tend to believe that they find shelter rather than fly between the raindrops.
Other people asked questions on similar topics, check out the answers they received:
Other people asked questions on various topics, and are still waiting for answer. Would be great if you can take a sec and answer them