Your know-it-all neighbor does, at least, know something about exterior painting. Paint when the temperature is above 60 and below 90 degrees F. Otherwise the drying time will be adversely affected. Avoid not only rain but also wind. High winds not only can cause your paint to dry too quickly, they can also blow dirt and other debris onto the wet surface. You should also try to paint with the shade. In other words, if you can avoid painting indirect sunlight, do so. Always check the manufacturer’s instructions on the paint can label and get advice from your local independent paint retailer.