A good, soft rain can actually activate some of the products we use, making them more effective. If we are spaying, then that may need another application. We monitor the weather to make sure we are using the products according to the directions on the label when it comes to any weather events. No matter what the weather, our techs have been trained to place the spray in sheltered spots where treatment will be done and under edges where the rain may not hit. So, often, we don't need to return before our next regularly scheduled visit.