Service call....rain in forecast.

I have a service call for Thursday morning, but the weather forecast calls for heavy rain all day. The service call is for relocating my dish. I don't think the installer will want to climb ladders and walk on roofs in a pouring rain. Do I call DTV and reschedule, or will the installer reschedule on their own? I don't really want them to *try* to do this in a pouring rain, only to rush the job. Advice?