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

Mosquito months in Los Alamos County

In a normal year mosquito season in Los Alamos County, NM starts around April 21 and ends around October 17, about 26 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 Los Alamos County, and when

• Start tipping out standing water weekly by April 7.
• Book any yard treatment for late April, ahead of the July peak.
• Repellent can go away after October 17.
• 1 West Nile case since 2016 (last 2023): you should use repellent at dusk July, more so if over 60.

Los Alamos County against the rest of NM

Los Alamos County has the 20th longest season of 33 NM counties, at 179 days against 268 in Doña Ana County and 114 in Catron County. Its mean temperature is 49.8°F.

• San Juan County: April 17 to October 25 (191 days, 49 WNV)
• Lincoln County: April 24 to October 24 (183 days, 3 WNV)
• Harding County: April 24 to October 20 (179 days, 0 WNV)
• Sandoval County: April 26 to October 20 (177 days, 18 WNV)

West Nile in Los Alamos County

From 1999 to 2025, CDC ArboNET counted 2 human West Nile cases in Los Alamos County (0 neuroinvasive) across 2 years. The worst was 2023 with 1; the latest was 2023.

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