Mosquito Season

It’s that time of year again, mosquito season. Are you ready? San Francisco’s Mosquito Abatement Courier Team (MAC) is! We’re treating catch basins across San Francisco to keep these little bloodsuckers at bay. Before you break out the bug spray or hang a bed net find out what’s happening and how you can help fight the bite this mosquito season.

When is the San Francisco Mosquito Season? It is year round with increasing activity from May through November. Luckily the City of San Francisco doesn’t have the same pressure of mosquitoes as our neighboring counties do thanks to our mild climate and favorable environmental conditions. However mosquitoes, especially the pesky Northern House Mosquito, Culex pipiens, are active year round in the City. These mosquitoes develop at temperatures above 50 degrees F, developing faster as temperatures increase. That means in San Francisco the peak of mosquito season is during the “Indian Summer” or more accurately our warm and sunny fall that typical starts in September and ends in November.

Some factors that may contribute to greater mosquito activity this mosquito season than previous years was the return of the rains and warmer temperatures early on. While the rains are good for flushing out our sewer and storm drain system the additional rain water collects in clogged gutters, old tires, and containers of all kinds on the outside of buildings, in parks, and vacant lots across the City. It doesn’t take much water at all for the house mosquito to breed in and if you hear or see a tiny mosquito buzzing around your head at night it’s very likely the house mosquito with a mosquito nursery nearby. However large bodies of stagnant water are capable of producing thousands of mosquitoes which can travel up to 2 miles away in search of a blood meal.

There are other species of mosquitoes that prefer natural bodies of standing water such as lakes, ponds, and dammed streams in SF parks & natural areas. These mosquitoes are attracted to the same triggers as the house mosquito: body heat, exhalations & body odor, and movement. They are generally most active at dusk and dawn so if you are exploring these areas at these times covering your body with long sleeves and pants is a good first step to protect yourself. The Center for Disease Control (CDC) recommends applying insect repellent to uncovered skin and according to the directions on the label of the product. The Environmental Protection Agency (EPA) lists all registered insect repellents, with hours of protection that the products claim here.

Article 11 Sec. 581 (a) of the San Francisco Health Code states that no person shall have upon any premises or real property owned, occupied or controlled by him or her, or it any public nuisance, including mosquitoes. Mosquitoes are a potential disease vector, meaning that they are capable of spreading diseases from infected animals to people. For this reason the San Francisco Public Utilities Commission Wastewater Enterprise (WWE) Collection System Division monitors and treats it’s nearly 24,000 storm drains during the mosquito season. To date there have been only two human cases of West Nile Virus infection in in San Francisco and both are suspected to have been contracted outside the City limits. WWE is doing its part to protect the residents and visitors of San Francisco from mosquito-borne illness. Join our team to help monitor mosquitoes and stay up to date with the services WWE provides for mosquito prevention.

Mosquito Season in the news:

SF Gate: Following winter rains, Bay Area mosquitoes threaten to swarm

KRON 4: Wet winter bring increased threat of mosquitoes

CBS Bay Area: California’s Rainy Winter Likely To Give Mosquito Populations A Boost

Mercury News: Mosquitoes ready to invade the Bay Area