Mosquito season in Sandoval County, NM: when it starts and ends

Mosquito months in Sandoval County

In a normal year mosquito season in Sandoval County, NM starts around April 26 and ends around October 20, about 25 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 Sandoval County, and when

• Start tipping out standing water weekly by April 12.
• Book any yard treatment for late April, ahead of the July peak.
• Repellent can go away after October 20.
• 18 West Nile cases since 2016: you should wear EPA-registered repellent at dusk July to August, and check NM spray notices.

Sandoval County against the rest of NM

Sandoval County has the 22nd longest season of 33 NM counties, at 177 days against 268 in Doña Ana County and 114 in Catron County. Its mean temperature is 51.2°F.

• Los Alamos County: April 21 to October 17 (179 days, 1 WNV)
• Harding County: April 24 to October 20 (179 days, 0 WNV)
• Union County: April 26 to October 17 (174 days, 4 WNV)
• Santa Fe County: May 3 to October 16 (166 days, 14 WNV)

West Nile in Sandoval County

From 1999 to 2025, CDC ArboNET counted 59 human West Nile cases in Sandoval County (36 neuroinvasive) across 11 years. The worst was 2003 with 19; the latest was 2025.

Background: reading the West Nile counts; how the dates are worked out.