Mosquito season in Platte County, WY: when it starts and ends

Mosquito months in Platte County

In a normal year mosquito season in Platte County, WY starts around May 9 and ends around October 1, 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 Platte County, and when

• Start tipping out standing water weekly by April 25.
• Book any yard treatment for early May, ahead of the July peak.
• Repellent can go away after October 1.
• 6 West Nile cases since 2016 (last 2023): you should use repellent at dusk July to August, more so if over 60.

Platte County against the rest of WY

Platte County has the 10th longest season of 23 WY counties, at 145 days against 163 in Big Horn County and 75 in Teton County. Its mean temperature is 49°F.

• Goshen County: May 9 to October 1 (145 days, 15 WNV)
• Laramie County: May 9 to October 1 (145 days, 11 WNV)
• Sweetwater County: May 12 to October 2 (144 days, 0 WNV)
• Natrona County: May 11 to October 1 (143 days, 12 WNV)

West Nile in Platte County

From 1999 to 2025, CDC ArboNET counted 82 human West Nile cases in Platte County (16 neuroinvasive) across 11 years. The worst was 2003 with 62; the latest was 2023.

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