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

Mosquito months in Cecil County

In a normal year mosquito season in Cecil County, MD starts around April 4 and ends around November 4, about 31 weeks.

What to do in Cecil County, and when

Start tipping out standing water weekly by March 21.
Book any yard treatment for early April, ahead of the July peak.
Repellent can go away after November 4.
5 West Nile cases since 2016 (last 2025): you should use repellent at dusk June to August, more so if over 60.

Cecil County against the rest of MD

Cecil County has the 19th longest season of 24 MD counties, at 215 days against 235 in Wicomico County and 175 in Garrett County. Its mean temperature is 55.4°F.

Charles County: April 2 to November 6 (218 days, 2 WNV)
Kent County: April 2 to November 6 (218 days, 2 WNV)
Harford County: April 5 to November 2 (211 days, 9 WNV)
Washington County: April 6 to October 31 (208 days, 3 WNV)

West Nile in Cecil County

From 1999 to 2025, CDC ArboNET counted 9 human West Nile cases in Cecil County (4 neuroinvasive) across 6 years. The worst was 2018 with 2; the latest was 2025.

See how the dates are worked out, and reading the West Nile counts.