Nothing to do with bank balance dazmond 
i just dont think its worth losing good customers by insisting on working in the rain .
I had two customers today ( one 32 quid 6 weekly, one 50 quid 8 weekly) who asked me not to clean there windows today as there are thunderstorms due and their windows will be dirty again tomorrow.
Would you insist on cleaning them today and risk losing them customers whether you thought there point was valid or not?
You should train them when you take them on. So you explain what kind of weather conditions you work in and why. "Because you are removing 4/8 weeks worth of dirt" .
I would kindly explain that while I don't work during thunderstorms. I don't believe that generally one thunderstorm will make windows dirty. It is the accumulation over 4/8 weeks along with birds muck snails trails and spiders poo that gets removed.
The fact that you have 6 weekly and 8 weekly customers also indicates to me that you give too many options.
£32 or £50 doesn't come into it. (You say "nothing to do with the bank balance" but there it is for all to see) How long it takes and how much I get messed about does.
For the record I only work in a maximum of drizzle or showery conditions; not to keep my customers happy but because I do not have the desire to. I am lucky in that I am happy with my monthly income and that I can do it in 3 days a week average. If I were younger, fitter and wanting to earn 50K a year instead of 30K then I would work in the rain or have an employee or two who would have to work in the rain for me to make a profit on their costs.