During which months are mosquitoes most active in Illinois?

Mosquitoes in Illinois are most active during the months of May to September. This period corresponds to the warm and humid conditions that are ideal for mosquito breeding and activity. During the late spring and summer months, temperatures rise, providing a favorable environment for mosquitoes to thrive. The presence of standing water from rainfall also contributes to the breeding sites needed for their larvae to develop.

The months of April to June do mark the beginning of their active season, but it's during May to September that the populations increase significantly, and they are more frequently encountered by humans. The other options—January to March and October to December—fall into colder seasons when temperatures drop and conditions become less suitable for mosquitoes to survive and reproduce. Thus, identifying May to September as the peak active months aligns with the biological and environmental factors influencing mosquito behavior in Illinois.