Street catch basins are a common tool for managing stormwater in urban areas and many municipalities responsible for their maintenance do not realize they produce mosquitoes during the summer months. Catch basins vary in size and two grated inlets are common regionally: the first is an open grate set into the street and the second is a smaller grate set into the vertical surface of the sidewalk with a solid metal cover for access to the basin. Catch basins were sampled to determine if grate type is associated with differences in mosquito density. Additionally, the association between catch basin design, water quality, mosquito seasonality, and species composition was evaluated by monitoring 60 catch basins on a weekly basis using modified dipping techniques. Two mosquito species, Culex pipiens Linnaeus and Culiseta incidens Thomson were commonly collected starting mid April.