The allergens hitting you hardest right now depend on the time of year and where you live. Tree pollen dominates from March through May, grass pollen peaks in late spring and early summer, and ragweed takes over from August through November. If you’re miserable and wondering what’s in the air, here’s a breakdown of what’s likely causing it and what you can do about it.
Spring: Tree Pollen Season (March to May)
Tree pollen is the first major wave of the year. Birch, oak, cedar, maple, and elm trees release massive amounts of pollen starting in early March in warmer climates and continuing through May in cooler regions. On high-count days, tree pollen can exceed 1,500 grains per cubic meter of air, which is classified as “very high.” Even moderate levels, starting around 15 grains per cubic meter, can trigger symptoms in sensitive people.
Birch pollen deserves special attention because it’s one of the most common tree allergens and triggers a reaction that goes beyond sneezing. If you’re allergic to birch pollen, you may notice tingling or itching in your mouth when eating raw apples, cherries, peaches, carrots, celery, almonds, or hazelnuts. This is called oral allergy syndrome. The proteins in those foods are structurally similar to birch pollen, so your immune system reacts to both. Cooking the food usually eliminates the problem.
Late Spring and Summer: Grass Pollen Takes Over
As tree pollen tapers off, grass pollen ramps up. This transition happens roughly from May into July, though it varies by region. Grass pollen counts are considered high at just 20 grains per cubic meter, a much lower threshold than trees, which means even moderate-looking forecasts can cause real symptoms. Bermuda, Timothy, Kentucky bluegrass, and ryegrass are among the worst offenders.
People with grass pollen allergies sometimes react to melons, oranges, tomatoes, and potatoes through that same oral allergy syndrome mechanism. If watermelon or cantaloupe makes your lips tingle during summer, grass pollen sensitivity is the likely reason.
Fall: Ragweed and Mold Season
Ragweed is the dominant allergen from August through November. A single ragweed plant can release up to a billion pollen grains in a season, and those grains travel hundreds of miles on the wind. Weed pollen counts hit “high” at 50 grains per cubic meter and “very high” at 500. If you’re sensitive to ragweed, you may also react to bananas, cucumbers, melons, and zucchini.
Fall is also peak season for outdoor mold spores. Decaying leaves and damp soil create ideal conditions, and mold spore counts can climb well past 13,000 spores per cubic meter (the threshold for “high”). Raking leaves or walking through wooded areas on damp days can trigger intense symptoms that feel indistinguishable from pollen allergies.
Winter Isn’t a Free Pass
Cold weather kills off most outdoor pollen, but indoor allergens pick up the slack. Dust mites thrive in warm, humid indoor air. Mold grows in any space where relative humidity stays above 60 percent, which is common in tightly sealed winter homes with poor ventilation. Keeping indoor humidity between 30 and 50 percent significantly reduces both mold growth and dust mite populations. A simple hygrometer from a hardware store can help you monitor this.
Pet dander also becomes more concentrated in winter because windows stay shut and air circulation drops. If your symptoms are worst at home and improve outdoors, indoor allergens are the likely culprit regardless of the season.
Allergy Seasons Are Getting Longer and Worse
If your allergies feel worse than they did a decade ago, they probably are. Warmer temperatures mean plants start pollinating earlier in the spring and continue later into the fall. Plants are also growing in areas where they previously couldn’t survive, introducing new allergens to regions that didn’t used to deal with them. Higher carbon dioxide levels in the atmosphere, largely from diesel exhaust, actually change pollen chemistry so that grains detach from plants faster and earlier. The result is more pollen, released over a longer window, reaching more people.
Thunderstorms make things even worse. During a storm, pollen grains get swept into clouds, absorb moisture, swell, and burst into tiny fragments. Those fragments are small enough to penetrate deep into the lungs, which is why some people experience sudden, severe asthma attacks during or just after a thunderstorm, even if they don’t normally have asthma. This phenomenon, known as thunderstorm asthma, is most dangerous during peak grass or ragweed seasons when pollen counts are already elevated.
Allergies, Cold, or COVID?
Spring and fall allergy symptoms overlap heavily with colds, flu, and COVID. The fastest way to tell them apart is to check for two things: itchiness and fever. Allergies almost always cause itchy eyes, nose, or inner ears. Colds and COVID rarely do. Allergies never cause a fever. If you have one, something infectious is going on.
Duration is the other major clue. A cold typically resolves within 3 to 10 days. Flu hits hard and fast, usually appearing 1 to 4 days after exposure. COVID symptoms can start anywhere from 2 to 14 days after exposure. Allergies, by contrast, last for weeks and follow pollen patterns: they’re worse on dry, windy days and better after rain. If your symptoms track with the weather rather than fading over a week or two, you’re dealing with allergies.
How to Check What’s in the Air Right Now
Local pollen and mold forecasts are available through weather apps, the National Allergy Bureau (pollen.com), and many local news stations. These forecasts report daily pollen counts broken down by type, so you can see whether trees, grasses, weeds, or mold are the current problem in your area. Knowing which specific pollen is elevated helps you plan: you might keep windows closed on high-count mornings, shower before bed to rinse pollen from your hair and skin, or time outdoor exercise for after a rainstorm when counts temporarily drop.
If over-the-counter antihistamines and nasal sprays aren’t controlling your symptoms, allergy testing can identify your exact triggers. Knowing whether you react to oak versus birch, or ragweed versus grass, lets you anticipate your worst weeks rather than guessing. It also opens the door to immunotherapy, which gradually reduces your sensitivity over time rather than just masking symptoms.