Mosquito season in Caroline County, MD: when it starts and ends

Mosquito months in Caroline County

In a normal year mosquito season in Caroline County, MD starts around April 1 and ends around November 9, about 32 weeks.

What to do in Caroline County, and when

Start tipping out standing water weekly by March 18.
Book any yard treatment for early April, ahead of the July peak.
Repellent can go away after November 9.
No West Nile cases since 2016, so bites in Caroline County are a nuisance; check window screens.

Caroline County against the rest of MD

Caroline County has the 11th longest season of 24 MD counties, at 222 days against 235 in Wicomico County and 175 in Garrett County. Its mean temperature is 56.3°F.

Baltimore County: March 30 to November 9 (223 days, 26 WNV)
Howard County: March 30 to November 8 (223 days, 1 WNV)
Queen Anne's County: April 1 to November 8 (221 days, 0 WNV)
Frederick County: March 30 to November 5 (220 days, 13 WNV)

West Nile in Caroline County

From 1999 to 2025, CDC ArboNET counted 2 human West Nile cases in Caroline County (2 neuroinvasive) across 2 years. The worst was 2004 with 1; the latest was 2004.

See how the dates are worked out, and when mosquitoes go away for the winter.