I have heard some home inspectors complain about having to do inspections in the rain when I was at a recent meeting.
Personally, I think it is the absolute best time to do a home inspection. I have been on a lot of home inspections, where the rain helps me find things that are leaking, pinpoint them, and take pictures to record the places where leaks are occurrring.
Conditions in a home cannot be duplicated by running a garden hose, and believe it or not things will leak during a rain that would never leak when just using a garden hose. Reason: you cannot duplicate the volume with a garden hose.
Gutters and underground drains will overflow and back up during even a medium rain sometimes, yet would never back up if you tried using a hose, because you cannot get the same volume all at once.
Roofs also will leak during a rain that would not otherwise as well... for the same reason, and also, because sometimes the wind also plays a part in some roof leaks.
Basement leaks can also be found during medium to heavy rains that would not otherwise be found. Again, the volume of soaking the ground around the foundation is many times what causes the leak to happen. A light rain or a garden hose might take several hours, or even days to duplicate the same conditions.
So, I say, let it rain. and maybe you even want to look a little closer at the forecast, and see if you can schedule your home inspection during a rainy time... it might be beneficial!
Also my est time to inspect any REO we are entertaining to buy. When its rain water intrusions and flow of ground water is very obvious.