I work in all weathers except high winds and torrential rain (mayb a few days in the year we get that).
If you havnt got a full work load then obviously you can pick and choose. If you have a decent size round then your customers would rather you be reliable and on time (but work in the rain) than hit or miss (but only work in the dry).
It's a constant cycle. We clean the Windows, they get dirty, we clean them again.
We could be working in lovely sunshine, and then it's terrible weather a few hours later. What's the difference?
Aslong as YOU don't mind working in the rain, then just crack on. Don't let the customers dictate how you run your business.