Ditto CTS.
I do the exact same thing as related to timing.

Over cast, has rained or is drizzling outside...Odds are good nobody will be at the outdoor range AND I _will_ be there.
I keep a poncho and pair of umbrellas including a large three man golf type one in my trunk perpetually year round, along with many range specific supplies including multiple targets and whatnottery.
Many times I've trained in a down pour shooting at hard (plastic pumpkin) targets with either a handgun or longgun. Guns work fine and are just as accurate when wet.
Oppositely on hot days and/or very nice folks wanna be out side days as well as mid day during the week, I'll go to the indoor range...And likely have the place to myself.

I've been doing it that way for ages. : )

- Janq