Mosquito season in St. Mary's County, MD: when it starts and ends
Mosquito months in St. Mary's County
In a normal year mosquito season in St. Mary's County, MD starts around March 26 and ends around November 15, about 33 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in St. Mary's County, and when
- Start tipping out standing water weekly by March 12.
- Book any yard treatment for late March, ahead of the July peak.
- Repellent can go away after November 15.
- No West Nile cases since 2016, so bites in St. Mary's County are a nuisance; check window screens.
St. Mary's County against the rest of MD
St. Mary's County has the 3rd longest season of 24 MD counties, at 234 days against 235 in Wicomico County and 175 in Garrett County. Its mean temperature is 58.5°F.
- Wicomico County: March 24 to November 15 (235 days, 1 WNV)
- Baltimore city: March 25 to November 15 (235 days, 18 WNV)
- Anne Arundel County: March 26 to November 13 (232 days, 12 WNV)
- Talbot County: March 26 to November 13 (232 days, 2 WNV)
West Nile in St. Mary's County
From 1999 to 2025, CDC ArboNET counted 1 human West Nile case in St. Mary's County (1 neuroinvasive) across 1 year. The worst was 2002 with 1; the latest was 2002.
Background: when mosquitoes go away for the winter; how the dates are worked out.