The combination of heat and humidity prompts the "heat index," the summer equivalent of the wind chill, and the recent spent of triple-digit heat index readings is doing more than making folks in the metro-area look for shade.

It also is prompting a wave of mosquitoes ready to annoy those spending the Fourth of July outdoors.

The weather in recent weeks creates the ideal recipe for hatching of the pesky insects.

In the fall, mosquitoes lay their eggs just above any water line they come across, especially in marshes and bogs. Then, the soupy combination of water rising above the eggs and heat prompts hatching of mosquito larvae.

Well, think about the last two weeks of weather. First came drenching rains, and then suffocating heat, which means next on tap is the slapping of mosquitoes and those sunset words: "I've got to go inside, the mosquitoes are bugging me."

But we all knew this was inevitable, right? After all, along with death and taxes, one may as well add mosquitoes to the inevitable for Minnesotans.

But the figures are fairly staggering. In the Twin Cities alone, folks at the Metropolitan Mosquito Control District say they have identified at least 60,000 breeding sites in the metro area. And with one acre able to produce one million mosquitoes a summer, you can do the math.

Officials say the combination means billions -- yes, billions -- of mosquitoes are expected to hatch in the coming days, just in time to start swarming unsuspecting swimmers, sun bathers and Fourth of July picnickers.

The mosquito control district folks began spraying a mosquito-killing bacterium on the breeding spots in April, and 160 workers have continued the spraying through May and June, but the are expected to hit only slightly more than one-half the breeding spots in the Twin Cities.

That means break out the mosquito spray, light up the citronella candles and get ready to start slapping.