“A perfect storm” of pollen production, as described by one horticulture expert, has Long Island allergy sufferers struggling to fall asleep and reaching for medications.

Normally, nature produces more of a sequencing of blooming trees and grasses, but weather conditions this year have led to a pollen pileup starting last week, said Vincent Drzewucki, horticulture resource educator at the Cornell Cooperative Extension of Nassau County.

With mild winter conditions, the area’s early blooming trees, such as maples, elms and birch, started doing their thing more or less on schedule — but were halted by a blizzard/ice storm in March and a string of colder days, he said. Those trees were delayed in blooming and picked up again in an off-and-on fashion as temperatures warmed and cooled, he said.

Pollen from those trees has been mingling with that of various types of oak that started blooming in May, he said. There’s also a grand slam scenario in place because some grasses are also at bat and starting to pollinate, he said.

Indeed, pollination of species that ordinarily flower at varying times has this year gotten “all bunched together,” said Jessica Gurevitch, a professor in Stony Brook University’s Department of Ecology and Evolution.

Sales in over-the-counter allergy medications certainly started picking up as of last week, said Kyle Kern, manager at Health Mart Pharmacy in Freeport. He said even before the increasing number of allergy-suffering customers reach the counter, he recognizes them by their “sniffling and red noses.”

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No one knows those symptoms better than Drzewucki, an allergy sufferer himself. As someone whose work regularly brings him outdoors, he keeps his over-the-counter medication close at hand. But on the rare day he’s without it, he says he’ll find himself with the telltale stuffy nose and eyes watering so badly he says he’s “almost blinded by the tears.”

He and others can look forward to some relief on Friday, as the weather forecast is for moderate to heavy rain, which is nature’s great air purifier, at least as far as pollen is concerned.