I have had the same problem with rain, as well as with breezy days. I' ve yet to find a way to solve the rain issue since there is no way to adjust sensitivity. Also, rain dripping from the trees after a shower can also trigger it.

The breezy days you can resolve by making sure you have no limbs or obstructions directly in front of the sensor out to about 20 yards. At least, that' s my experience.