Weekly Update – July 28th – Mosquitoes Stay Low Heading Into August
July 28, 2026
Mosquito numbers are likely to stay at or below average for the rest of the year.
We finally saw some much needed rain last week, but it's not likely to make a big impact in mosquito numbers.
Last Thursday and Friday the Twin Cities saw more than an inch of rain for the first time in several weeks. It takes about 5-7 days for mosquitoes to go through their life cycle and go from egg hatch to adult emergence, so any mosquitoes that resulted from the rain are not likely to show up until next week's collections (which will be published the week after). Over the weekend, MMCD staff worked to determine where mosquito larvae developed and we identified almost 5,000 acres in large wetlands that will be treated by helicopter.
Even with that rain and the fresh larvae that emerged, we are not likely to see the overall average for the District surge much higher than the 10-year average in coming weeks. Most of the state is still facing drought conditions and meteorologists have stated that we would need 10 inches of rain just to get back to normal. There is not much rain in the forecast and August is looking to be dry like July so far.
Here are the maps for mosquitoes collected on Monday-Tuesday, July 27-28th:
Decline in Culex tarsalis mosquitoes week-to-week is good news for West Nile virus risk
Last week we saw a brief surge of Culex tarsalis mosquitoes collected in traps, but this week the numbers are back down again to fewer than one mosquito per trap. This is good news as we head into the time of year when West Nile virus is most active as Cx. tarsalis are the species that is most likely to transmit West Nile to humans.
According to MMCD Entomologist, Dr. Scott Larson, "Other Culex species are widespread at the moment even if their numbers aren't particularly bad, so there's potential WNV risk in most parts of the District."
The Vector Index saw a dip this week, but we are still before the time of year when we typically see a surge in vector activity based on the 5- and 10-year averages:
Screenshot from a Beta version of the new Vector Index.
Helicopters Active Today to Treat Areas with Mosquito Larvae
Last week's rain was enough to hatch another brood of mosquitoes - the first one we've experienced since early July. Helicopters are active today and may continue to tomorrow to treat areas of standing water with active mosquitoes. As always, the full list of cities is published on our Helicopter Activity page.
From here on out, helicopters will be active whenever there is an inch of rain or more to hatch mosquito larvae. As we head into the fall, we will begin doing surveillance for cattail mosquitoes and there will be some fall treatments based on where those are developing.
Upcoming Events
Come out and see staff from the Metropolitan Mosquito Control District at one of these upcoming events:
- Tuesday, August 4th - National Night Out Events in St. Francis, Nowthen, and West Lakeland Township
- Thursday, August 6th - Bugology at Sally Manzara Nature Center - Lake Elmo
- Thursday, August 6th - Empire City Celebration - Empire
- Friday, August 7th - Sunday, August 9th - Game Fair - Ramsey
- Saturday, August 8th - Stockyard Days Parade - New Brighton
Would you like MMCD to come to your event or speak to your group? E-mail Alex Carlson!
Article of the Week - Star Tribune Update on Mosquitoes
Mosquitoes were featured on the front page of the Sunday Star Tribune! The article "You’re not imagining it. There are fewer mosquitoes in Minnesota this summer" talks about how the various factors, mainly drought, have impacted this year's mosquito numbers.
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