There are several reasons why adulticide applications are made at night. 1) The majority of mosquito species are most active around dusk and again at dawn. We want to spray when mosquitoes are most likely to be out and flying. 2) In order for the spray droplets to remain close to the ground, applications must be made during a thermal inversion. This climatic condition normally occurs at night as ground temperature cools. Applications made during the middle of a hot day will be carried by rising currents of warm air straight up into the atmosphere. 3) Our citizens are less likely to be out and about after dark. While there is an extremely small risk associated with the adulticides we spray, BCMA strives to reduce human exposure as much as possible.