As many Alaskans rejoice with the return of leafy vegetation, others are sniffling and sneezing as allergy season begins.

Kicking off in spring, tree pollen fills the air shortly after leaves return. A little later, grass, mold and weeds attack allergy sufferers, but the difference in timing means different impacts from different weather.

Tree Pollen

Tree pollen is our worst allergy-inducer in the spring. Even before leaves are fully spread, tree allergens reach levels high enough to prompt concern for many. Depending on the weather, they can rise or fall to different levels of severity.

Moisture in the atmosphere weighs down the microscopic bits of tree pollen. On a humid day, the particles sink to the ground faster, not traveling as far after they are released from a tree. A light rain can wash the atmosphere free of tree pollen, the moisture weighs down the tiny pollen particles, bringing them to the ground where they come to a rest, no longer filling the air we breathe.

In dry weather, however, trees tend to release more pollen. If it’s windy, that pollen released into the air can travel much farther and affect more people.

Grass, Mold, and Weeds

 Grass, mold and weeds are different beasts. They peak later in the season, sometimes after tree pollens have already come and gone, and because they originate closer to the ground, they behave differently in different types of weather.

Rain drops hit the ground and break up the grass and weed pollen. The broken-up pollen is then pushed into the air, increasing allergy symptoms for sufferers. The heavier the rain, the more the pollen is broken up and pushed into the air.

As moisture levels in the atmosphere increase, mold and dust mite counts often rise. Both mold and dust mites thrive in humid conditions. Mold grows in warm, damp conditions. Dust mites multiply in the presence of humidity.


The perfect weather for allergy sufferers varies by season. No matter the time of year, wind can make allergies worse by spreading allergens from their place of origin. So, calm conditions are ideal. 

Spring showers can help knock down tree pollen. So if you suffer from tree pollen allergies and you want to get outdoors, try doing so after a light rain. Even smaller amounts of moisture, like higher humidity, can make a little difference in pollen count. That small difference might be enough to keep some of the worst symptoms at bay.

By mid-summer, things change. They key is weather that’s dry, but not so dry that the atmosphere is filled with dust. Dry air quells mold production and dust mite population growth. The lack of heavy rain keeps grass pollens in clumps and on the ground. Ideally, a quick, light rain during the heat of summer is all you want if you’re looking to stay allergy-free.

Copyright 2019 KTVA. All rights reserved.

Editor's note: This story has been updated to reflect the latest pollen counts.