All of the products we use on the exterior of the home to kill insects take up to 1-hour to dry. Once they are dry they will not be able to be washed off by the rain. We reschedule appointments while it’s raining, but if the product has an hour to dry, it will still effectively kill any insects that cross over the treated areas even if it rains on the same day. Each product we use will stay affective for up to 2 months after an application.