Mosquito season in Coconino County, AZ: when it starts and ends

Mosquito months in Coconino County

In a normal year mosquito season in Coconino County, AZ starts around May 15 and ends around October 12, 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 Coconino County, and when

• Start tipping out standing water weekly by May 1.
• Book any yard treatment for mid May, ahead of the July peak.
• Repellent can go away after October 12.
• No West Nile cases since 2016, so bites in Coconino County are a nuisance; check window screens.

Coconino County against the rest of AZ

Coconino County has the 15th longest season of 15 AZ counties, at 150 days against 364 in Maricopa County and 150 in Coconino County. Its mean temperature is 48.3°F.

• Navajo County: May 1 to October 20 (172 days, 7 WNV)
• Apache County: May 7 to October 17 (163 days, 4 WNV)

West Nile in Coconino County

From 1999 to 2025, CDC ArboNET counted 9 human West Nile cases in Coconino County (5 neuroinvasive) across 6 years. The worst was 2015 with 2; the latest was 2015.

Background: when the season starts across the US; how the dates are worked out.