Tom,
I know who mean and think a guarantee or insurance payment would work better in a residential market, I think this is mainly where he applies it. As you know residential is less price competitive, it might tip the balance the wrong way on commercial. If the subject of weather comes up everybody wants a cleaning in good weather, nobody understands trying to keep a schedule and run a business.
I do offer a rain guarantee if I face any opposition to bad weather and have not had to go back yet but overall find it better not to mention it unless necessary.