Mosquito season in Penobscot County, ME: when it starts and ends

Mosquito months in Penobscot County

In a normal year mosquito season in Penobscot County, ME starts around May 8 and ends around October 5, about 21 weeks.

1. Jan
2. Feb
3. Mar
4. Apr
5. May
6. Jun
7. Jul
8. Aug
9. Sep
10. Oct
11. Nov
12. Dec

What to do in Penobscot County, and when

• Start tipping out standing water weekly by April 24.
• Book any yard treatment for early May, ahead of the July peak.
• Repellent can go away after October 5.
• No West Nile cases since 2016, so bites in Penobscot County are a nuisance; check window screens.

Penobscot County against the rest of ME

Penobscot County has the 11th longest season of 16 ME counties, at 150 days against 164 in Kennebec County and 133 in Franklin County. Its mean temperature is 42.4°F.

• Hancock County: May 7 to October 10 (155 days, 1 WNV)
• Waldo County: May 8 to October 10 (155 days, 1 WNV)
• Oxford County: May 8 to October 4 (149 days, 0 WNV)
• Aroostook County: May 11 to October 1 (142 days, 0 WNV)

West Nile in Penobscot County

CDC ArboNET lists no human West Nile cases for Penobscot County from 1999 to 2025, though virus turned up in birds, mosquitoes or horses in 7 of those years.

See how the dates are worked out, and when the season starts across the US.