Do Seasons Affect Allergies? What Triggers Symptoms Each Season

Yes. Different plants release pollen at different times of year, outdoor mold rises and falls with warmth and moisture, and in winter you spend more time indoors with dust mites and pets. Weather adds another layer: the American Academy of Allergy, Asthma and Immunology (AAAAI) says hay fever is often milder on rainy, cloudy or windless days, while hot, dry, windy weather helps pollen travel.

Not every seasonal sniffle is an allergy, though. Changes in the weather can also trigger nonallergic rhinitis, which looks like hay fever but isn’t caused by allergies. This guide walks through each season and explains how to tell the difference. For more, see our seasonal and pollen allergy guides.

Jump to: Quick answer · Season by season · How weather changes symptoms · Longer pollen seasons · When it isn’t an allergy · Plan ahead · FAQ

Quick answer

• Early spring: tree pollen.
• Late spring and early summer: grass pollen.
• Late summer and fall: weed pollen, especially ragweed, which peaks in mid-September.
• Mold: outdoor mold spores peak in July in warmer U.S. states and in October in colder ones, and are found year-round in the South and on the West Coast.
• Winter: indoor allergens such as dust mites and pet dander, which are present all year.
• Seasons are getting longer: across North America, pollen seasons grew about 20 days longer from 1990 to 2018.

Allergies season by season

Exact timing depends on where you live and the weather that year. An allergist can test which pollens and molds you react to, so you know which season to prepare for.

Winter allergies

Outdoor pollen is low in most of the U.S. in winter, but allergies don’t always take a break. Dust mites live in bedding and carpets year-round, and pet dander builds up when animals spend more time inside. See our guides to sleeping better during allergy season, how common dust mite allergy is and why Christmas trees can make you sneeze.

Dry winter air also irritates the nose. A humidifier can help, but keep indoor humidity between 30% and 50%, as Mayo Clinic recommends, because damp air feeds dust mites and mold. Read humidifiers and flu for safe use.

How weather changes your symptoms

• Hot, dry, windy days: pollen travels more, which can increase symptoms (AAAAI). Mayo Clinic suggests staying indoors on dry, windy days.
• Rainy, cloudy or still days: hay fever symptoms are often less noticeable (AAAAI). ACAAI notes rain temporarily clears pollen from the air.
• Thunderstorms in grass season: storms can burst pollen grains into fragments small enough to reach the lungs, which can trigger asthma, even in some people never diagnosed with it. See what pollen looks like up close.
• Heat and humidity: help mold grow (ACAAI). Our mold and humidity guides cover indoor mold.
• Ozone alerts: ozone is a lung irritant that can worsen asthma. See air quality and summer asthma.

Pollen seasons are getting longer

A 2021 study in the Proceedings of the National Academy of Sciences analyzed pollen data from 60 North American stations from 1990 to 2018. Pollen seasons started earlier and lasted about 20 days longer, and pollen concentrations rose about 21%, closely tied to warming temperatures. The researchers estimated that human-caused climate change contributed about half of the trend in season length.

AAAAI adds that rising temperatures and carbon dioxide are making spring arrive earlier, and that ragweed grows faster and produces more pollen per plant. In practice, that means starting your allergy plan earlier than you might have years ago.

When seasonal symptoms aren’t an allergy

If a weather change sets off sneezing or a stuffy, runny nose, you may have nonallergic rhinitis. Mayo Clinic explains that it looks like hay fever but isn’t caused by allergies, and that its triggers include weather changes, irritants in the air like dust and fumes, some medicines, and hot or spicy foods.

Some clues help tell them apart:

• Itching: nonallergic rhinitis usually doesn’t cause an itchy nose, eyes or throat, which are typical of hay fever.
• Timing: nonallergic rhinitis symptoms often come and go all year rather than following a pollen season.
• Testing: skin or blood allergy tests are negative in nonallergic rhinitis. Doctors often test first to rule out allergies.

The treatments differ, so it’s worth finding out which one you have.

Plan ahead for each season

1. Start medicine early. AAAAI says hay fever medicines work best when begun before you first meet the season’s allergens.
2. Watch pollen and mold counts and stay inside when they are high (AAAAI).
3. Keep windows closed at home and in the car, and use air conditioning, which cleans, cools and dries the air (AAAAI).
4. Shower, shampoo and change clothes when you come back indoors (AAAAI).
5. Let someone else mow and rake (AAAAI).

For a full checklist, see our pollen avoidance guide. If symptoms last for months or come with wheezing, see an allergist about testing and longer-term treatment.

This guide is general information, not medical advice. Read our medical disclaimer.

Frequently asked questions

Why do I get allergies when the seasons change?

Each season brings different airborne triggers: tree pollen in early spring, grass in late spring and early summer, weeds like ragweed in late summer and fall, and mold in warm, damp weather. Weather changes can also trigger nonallergic rhinitis, which mimics allergies.

Which season is worst for allergies?

It depends on what you’re allergic to. Tree-allergic people suffer in early spring, grass-allergic people in late spring and early summer, and ragweed-allergic people in late summer and fall. An allergy test tells you which season to plan for.

Can weather changes cause allergy symptoms?

Weather changes can make allergies worse by spreading pollen (hot, dry, windy days) or feeding mold (heat and humidity). They can also directly trigger nonallergic rhinitis, which causes similar nasal symptoms without an allergy.

Can you have allergies in winter?

Yes. Dust mites, pet dander and indoor mold are present year-round, and you’re indoors more in winter. Outdoor mold can also be found year-round in the South and on the West Coast.

Are allergy seasons getting worse?

In North America, yes: a 2021 study found pollen seasons became about 20 days longer and pollen levels about 21% higher between 1990 and 2018, largely linked to warming.

Sources

• American Academy of Allergy, Asthma and Immunology. Outdoor allergens.
• American Academy of Allergy, Asthma and Immunology. Climate change and outdoor allergies.
• American Academy of Allergy, Asthma and Immunology. Controlling hay fever symptoms.
• Anderegg WRL, Abatzoglou JT, Anderegg LDL, et al. Anthropogenic climate change is worsening North American pollen seasons. Proc Natl Acad Sci U S A. 2021;118(7):e2013284118.
• American College of Allergy, Asthma and Immunology. Seasonal allergies and Ragweed allergy.
• Mayo Clinic Staff. Nonallergic rhinitis: Symptoms and causes. November 6, 2025.
• Mayo Clinic Staff. Hay fever: Diagnosis and treatment.

Last reviewed: October 21, 2026.