Mosquito season in Northumberland County, PA: when it starts and ends
Mosquito months in Northumberland County
In a normal year mosquito season in Northumberland County, PA starts around April 17 and ends around October 21, about 27 weeks.
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
What to do in Northumberland County, and when
- Start tipping out standing water weekly by April 3.
- Book any yard treatment for mid April, ahead of the July peak.
- Repellent can go away after October 21.
- 4 West Nile cases since 2016 (last 2023): you should use repellent at dusk July to August, more so if over 60.
Northumberland County against the rest of PA
Northumberland County has the 31st longest season of 67 PA counties, at 187 days against 222 in Philadelphia County and 154 in Clinton County. Its mean temperature is 50.4°F.
- Bedford County: April 16 to October 20 (187 days, 1 WNV)
- Montour County: April 17 to October 21 (187 days, 1 WNV)
- Schuylkill County: April 17 to October 21 (187 days, 4 WNV)
- Lackawanna County: April 18 to October 21 (186 days, 4 WNV)
West Nile in Northumberland County
From 1999 to 2025, CDC ArboNET counted 9 human West Nile cases in Northumberland County (8 neuroinvasive) across 5 years. The worst was 2003 with 4; the latest was 2023.
See how the dates are worked out, and reading the West Nile counts.