There is an upside to this spring's persistently cool and cloudy conditions: The mosquito population is way down — at least so far.

With the lack of sustained warmth in May, mosquito larvae have been slower to develop than in past years, said Mike McLean, a spokesman for the Metropolitan Mosquito Control District. That bodes well for a Memorial Day weekend with much less slapping and swatting.

"There are a few floating around out there, but large numbers have not appeared," McLean said. "We are catching a break due to the weather."

Conditions have been about right, too, for the mosquito police to get out in front of the first big batch. As of midweek, the district had treated 35,000 acres in the seven-county metro area by dropping granular pellets laced with a bacterium called Bacillus thuringiensis israelensis. Larvae ingest the tiny pellets and die on the spot, McLean said.

Over the next week, the district will continue treatment of wetlands — with helicopters in the air and personnel on the ground — to keep larvae from hatching. But that won't be an easy feat. Copious rains led to ample standing water, and as the temperature trends warmer next week, that could bring a sudden surge in the number of the biting pests.

"We have got a window of opportunity to do our treatments," said McLean, who expects the season to produce an average number of mosquitoes. "We try to keep them under control so people can enjoy their backyards."

The district plans to treat 150,000 to 200,000 acres this summer, but people can also help. McLean recommends emptying water-filled receptacles that can turn into breeding grounds, such as trash bins and old tires. Those mosquitoes "will be the ones later in the summer that can spread diseases," McLean said.

In Minnesota, mosquito-borne diseases include the West Nile and La Crosse encephalitis viruses.

To protect from mosquito bites, people should apply insect repellent and wear long pants and long-sleeved shirts, the U.S. Centers for Disease Control and Prevention advises.