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

Mosquito months in Maricopa County

In a normal year mosquito season in Maricopa County, AZ starts around January 5 and ends around January 4, about 52 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 Maricopa County, and when

• Start tipping out standing water weekly by December 22.
• Book any yard treatment for early January, ahead of the July peak.
• Repellent can go away after January 4.
• 1,999 West Nile cases since 2016: you should wear EPA-registered repellent at dusk April to October, and check AZ spray notices.

Maricopa County against the rest of AZ

Maricopa County has the 1st longest season of 15 AZ counties, at 364 days against 364 in Maricopa County and 150 in Coconino County. Its mean temperature is 73.1°F.

• Pinal County: January 8 to December 26 (352 days, 154 WNV)
• La Paz County: January 7 to December 21 (348 days, 2 WNV)

West Nile in Maricopa County

From 1999 to 2025, CDC ArboNET counted 3,155 human West Nile cases in Maricopa County (2,032 neuroinvasive) across 23 years. The worst was 2021 with 1,476; the latest was 2025.

See how the dates are worked out, and where mosquitoes never stop.