Let the sneezing, sniffling and itching of eyes begin.

The record-setting warm weather, which is likely to continue through the weekend, has given a jump start to the allergy season. Tree pollen, normally not a factor until the end of March or even early April, already is in the air.

"The trees are confused," said Dr. Gary Berman, an allergist in the downtown Minneapolis office of Allergy & Asthma Specialists. "We're talking about temperatures in the 70s and 80s. We usually still have snow on the ground."

As strange as the weather is, some of the advice being offered by allergists sounds even stranger, said Dr. James Li, chairman of the allergy and immunology department at the Mayo Clinic.

"One of the things people can do to avoid the pollen is go inside, close all the windows and turn on the air-conditioning," he said, adding: "It seems odd to be telling people to turn on the air-conditioning in the middle of March."

About 25 percent of the population suffers from seasonal allergies, although not everyone reacts to the same triggers. The four biggest culprits are tree pollen (spring), grass (summer), ragweed (fall) and mold (winter).

There's also more than the usual amount of dust in the air, which, although not directly related to allergies, isn't making breathing any easier, said Lori Litzinger, lead nurse at MN Allergy & Asthma Clinic, P.A., in Burnsville.

"There's been a lot of dust blowing around because it's been so dry," she said. "We haven't had any rain to settle it out."

She said that the early arrival of the pollen even caught the experts by surprise. The system for measuring and posting daily pollen counts isn't active this early in the year.

"So there is no official pollen count," she said, "but we know it [the pollen] is there."

Molly Peterson knows it, too. She was at the downtown Minneapolis Target store buying allergy medicine Friday morning, and she wasn't alone. By noon, several of the slots for the antihistamines billed as "non-drowsy" had been picked clean by office workers.

"I knew it [was allergy season] when I got up this morning and my nose stuffed-up solid," she said.

That quick onset of symptoms is one of the signs of an allergy. With the allergy season coming right on the heels of winter's cold and flu season, figuring out what's ailing you is important to treating it. Here are a few other guidelines: If you have a fever or over-all achiness, think cold, but itchiness in the eyes, nose or throat usually is a sign of allergies. Cold symptoms don't fluctuate much, but the severity of allergy symptoms can change dramatically based on your immediate surroundings. Thus, Li's advice about turning on the air-conditioning.

And -- if you're eating breakfast, you might want to skip this paragraph -- you can check the mucus coming from your nose. It will be clear with allergies but often have a foggy, yellow hue with a cold.

In areas south of Minnesota, the tree pollen arrived on time this year, but with much higher volume. Pollen counts in Des Moines and Omaha, Neb., are already listed as "high" and are predicted to reach "very high" -- that's as far up as the scale goes -- by early next week. But it's not a given that we can expect the same.

"The last week or so we've been seeing higher-than-usual pollen counts in those places where they already are into the season," Li said. "But it's still too early to make any predictions for here. The weather over the next four to six weeks will have a lot to do with it."

Nor are the experts willing to predict how long it will last. Asked if the spring season's start would be offset by an early end, Berman quipped, "Ask me in eight weeks." He added: "These seasons tend to be very regular -- until they're not. It might end early, but it could go until it normally ends."

The unusual weather will be much in evidence this weekend. Friday's high temperature of 79 was another record high for the date for the Twin Cities, the fifth since Saturday. That's 38 degrees higher than normal, a departure Minnesota DNR state climatologist Greg Spoden called "astounding."

Friday's warmth was also notable for a surge in dew points toward summery levels. The dew point Friday afternoon reached a muggy 57 in the Twin Cities, where it had been 29 only 24 hours before, and 63 at Hutchinson. A dew point of 60 in March has been recorded only once in the Twin Cities, on March 24, 1945.

In the worst case scenario, allergy suffers will need to keep tissues at the ready until the first hard frost of fall.

"Even if the tree pollen season ends early, it likely will overlap with the grass season," Li said. "And that can overlap with the ragweed. For a lot of people, I think it's going to be a very long allergy season."

Staff writer Bill McAuliffe contributed to this report. Jeff Strickler • 612-673-7392