My wife and I did the Essex Countryside 60 miler a couple of weekends ago. When we got up, the rain was so torrential that I got soaked just walking to the garage to get the bikes out. We just laughed, accepted that we were going to get soaked, strapped the bikes to the rack and got on with it.
By about 10 miles into the ride, it was warm enough to remove the waterproof jackets and an hour or so later, I thought we were going to get sun burn.
The heavens opened about 10 miles before the finish but we were having such a good time, we didn't even stop to put the macs back on. It was only a brief shower so we dried out anyway.
A good few of my mates gave this event a miss because they saw the weather in the morning. They were actually the losers. I think we just have to accept that rain is a fact of life and most certainly a fact of cycling life. Once you're over that mental hurdle, you can just get on with enjoying your cycling - whatever the weather.
Personally, I love those real nasty days where you get out and just get on with it. By the time you reach the coffee stop, you feel like you've really earned it (and a slice of cake).