I'm with a lot of the "ole' timers", I shoot whenever I can and just make the most of it. I dont worry much about it if I'm shootin' groups at 100yds. Only if it's raining harder than a drizzle, or the outside temp. is approaching 100 degrees.
I think the conditions that are present when a light drizzle is occuring are almost perfect for shooting. When the temps get up there you have to fuss with the barrel. I shoot once or twice and take my rifle inside for 15-20 minutes. Not sure this is actually the best method (metal expansion) but keeps the barrel from getting too hot. I keep my test loads inside until I'm ready to shoot 'em.
If I'm going to be shooting farther than 100yds I will go on-line and get an accurate weather forecast with as much info as I can get and plug everything into JBM. Barometric pressure, temp., wind, humidity, actual velocity for that day, it all matters, I feel.
It helps that I have a range at home. This setup makes load development quick, in-depth and stress free (for me). I don't like doing load development at home and then having to drive to the range to test them out. I'm left hanging until I get back to the range. At home I can shoot all day long, varying components, seating depths (if needed) and clean my barrels as I go. Perfect setup for OCD people.
Shoot when you can, work when you have to. JohnnyK.