Just send them out working in the rain, I have always done this residential and commercial, never been a problem, I think I lost two days last year to bad weather snow and this was only because I didn't want the vans getting written off, we usually work in the snow as well.
Other windies may have issues about this, but all I can say is that in all the years I've employed and been in business working in bad weather has never been an issue
Hope this helps