The sun is shining here now but no work today. I lost a customer recently because they said it wasn't worth having them done, I sympathise with them, I wouldn't want my windows cleaned either if they were going to be just as bad in a couple of hours.
I will work in moderate rain as the job is usually OK, but I don't think it's fair to clean windows during stormy weather.
Just go out and clean your van windscreen, then inspect it 3 hours later.
I live half a mile from the sea, but even with an offshore wind the windows are minging next day. Dai