Here in the Upper Midwest, I'm actually more likely to ride in the rain when it's the cold, gross rain. During the warm season, there are enough non-rainy hours of daylight to get miles in without dealing with wet weather, and rain is often accompanied by storms with lightning, wind, and hail. During transitional seasons, rain might be the best thing I've got, especially when daylight is limited, country drivers get squirrelly, and snow is coming or going.
Commuting is a different story (rain is fine in that case).