We clean in the rain. Obviously not if it's p***ing down, even I dont want to get that wet...but if it's just spitting or drizzly, then yeah. We promise a reliable regular service to our customers, and that's what they get. I've been sent away by the odd one, but most are fine, in fact they are mostly out at work, and my system is to leave a stamped addressed envelope and invoice, I'm paid mostly by cheque.
At the end of the day, I'm removing a months build up of crap off of the glass...which is exactly what I promised to do in the customer charter, which they all get.