Mosquito season in Norfolk County, MA: when it starts and ends
Mosquito months in Norfolk County
In a normal year mosquito season in Norfolk County, MA starts around April 15 and ends around October 23, about 27 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Norfolk County, and when
- Start tipping out standing water weekly by April 1.
- Book any yard treatment for mid April, ahead of the July peak.
- Repellent can go away after October 23.
- 6 West Nile cases since 2016 (last 2024): you should use repellent at dusk July to August, more so if over 60.
Norfolk County against the rest of MA
Norfolk County has the 3rd longest season of 14 MA counties, at 191 days against 194 in Plymouth County and 163 in Berkshire County. Its mean temperature is 51.9°F.
- Plymouth County: April 20 to October 31 (194 days, 5 WNV)
- Suffolk County: April 19 to October 29 (193 days, 18 WNV)
- Nantucket County: May 1 to November 2 (185 days, 0 WNV)
- Bristol County: April 23 to October 24 (184 days, 8 WNV)
West Nile in Norfolk County
From 1999 to 2025, CDC ArboNET counted 17 human West Nile cases in Norfolk County (13 neuroinvasive) across 10 years. The worst was 2012 with 3; the latest was 2024.
See how the dates are worked out, and reading the West Nile counts.