No I never look for them, i just make sure all my custy's know I do guttering, its also printed on all my tickets I put through there doors, last year was my best year for guttering work and it was all down to the rain.
Just mention to your custy's that you offer this service, I also do conservatory roofs in the rain, unless custy wants it done there and then.
Both good little earners for rainy days, the only thing I don't like is the wet weather gear, makes you sweat like a glass blowers a***