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

Mosquito months in Union County

In a normal year mosquito season in Union County, NM starts around April 26 and ends around October 17, 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 Union 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 17.
• 4 West Nile cases since 2016 (last 2023): you should use repellent at dusk July to August, more so if over 60.

Union County against the rest of NM

Union County has the 23rd longest season of 33 NM counties, at 174 days against 268 in Doña Ana County and 114 in Catron County. Its mean temperature is 51.9°F.

• Harding County: April 24 to October 20 (179 days, 0 WNV)
• Sandoval County: April 26 to October 20 (177 days, 18 WNV)
• Santa Fe County: May 3 to October 16 (166 days, 14 WNV)
• Torrance County: May 5 to October 10 (158 days, 3 WNV)

West Nile in Union County

From 1999 to 2025, CDC ArboNET counted 6 human West Nile cases in Union County (2 neuroinvasive) across 3 years. The worst was 2023 with 4; the latest was 2023.

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