Mosquito season in Carroll County, MD: when it starts and ends
Mosquito months in Carroll County
In a normal year mosquito season in Carroll County, MD starts around April 9 and ends around October 29, about 29 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Carroll County, and when
- Start tipping out standing water weekly by March 26.
- Book any yard treatment for early April, ahead of the July peak.
- Repellent can go away after October 29.
- 4 West Nile cases since 2016 (last 2025): you should use repellent at dusk June to August, more so if over 60.
Carroll County against the rest of MD
Carroll County has the 23rd longest season of 24 MD counties, at 203 days against 235 in Wicomico County and 175 in Garrett County. Its mean temperature is 53.1°F.
- Washington County: April 6 to October 31 (208 days, 3 WNV)
- Allegany County: April 6 to October 28 (205 days, 0 WNV)
- Garrett County: April 24 to October 16 (175 days, 0 WNV)
West Nile in Carroll County
From 1999 to 2025, CDC ArboNET counted 6 human West Nile cases in Carroll County (5 neuroinvasive) across 3 years. The worst was 2025 with 2; the latest was 2025.
More: how the dates are worked out · reading the West Nile counts.