Warm temperatures and heavy rain during a short time period, generally means more mosquitoes. If rainfall is spread over a wide area, it makes it more difficult for all areas to be reached with our larval control before the larvae become adult mosquitoes. Sometimes closely spaced rains will produce more than one brood (or hatch) of mosquitoes in the water at the same time. Consequently, some sites will have to be treated twice, and we may not have enough time and resources to do this. Conversely, normal rainfall or a dry period generally means fewer mosquitoes, and populations are easier to control.