I've been a trad shiner for 30yrs and I've worked in the rain when I've needed to, though not torrential rain.
I've found Alex's last argument quite useful in educating my customers to expect that if I need to work in the rain then it's not unreasonable.
However, I've never forced the issue as I know some do. I just tell them I'll see them next month and move on to the next customer. Some don't like it when I don't go back and do them the following day and I've lost a handful of customers over it. However as LWC pointed out, the bills don't stop comming in when it rains, so why should we stop working if we need to.
I'd imagine using the 'wfp' method will help in this regard for reasons already mentioned in this thead.
Anyways, best regards all,
Mark