You need few things to see a rainbow. The main thin is rain, you need that rain to be in illuminated by bright sunshine, and you need to be in a position that the rain lies on the circle 42 degrees around the shadow of your head. So if you get rain from a shower that moves in the direction away from the sun relative to you then you have a good chance of seeing a rainbow. You are most likely to see rainbows on days with scattered shower or storms than on dull overcast rain days.