Depends how they do it. If they’re old fashioned and use soapy water then yes, you’re right. If they use modern purified water systems then it’s all good. Doesn’t matter if it rainsYes. However, every time they visit it pees down the next day.
Albeit, I'm hoping they turn up soon as the garden is brown.
I know this sounds sarcastic, but you pay for windows to be cleaned and when they rock up and it’s peeing down. It’s like washing a car when it’s raining.