Yes, allergy season is almost always underway somewhere in the United States. Pollen from trees, grasses, or weeds circulates from as early as February through the first hard frost, which in some regions doesn’t arrive until mid-December. The real question is which allergens are active right now and whether they explain what you’re feeling.
The Three Pollen Seasons
Allergy season isn’t one event. It’s three overlapping waves, each driven by a different plant group.
- Trees (February through April): The first wave. In warmer parts of the South and West Coast, tree pollen can appear as early as December or January. The biggest offenders include oak, birch, cedar, juniper, elm, maple, and cottonwood.
- Grasses (April through early June): Timothy, Bermuda, Kentucky bluegrass, ryegrass, and fescue are among the most common triggers. Grass pollen overlaps with the tail end of tree season, so late April and May can hit especially hard.
- Weeds (August through first frost): Ragweed dominates this stretch, releasing pollen from August to November. It grows almost everywhere but is especially prevalent on the East Coast and across the Midwest. Other fall culprits include sagebrush, tumbleweed, and pigweed.
In tropical climates like Florida and the Gulf Coast, grass and other plants bloom through most of the year, so seasonal allergies can be a nearly year-round problem.
Fall Adds Mold to the Mix
Weed pollen isn’t the only fall trigger. Outdoor mold spores become more concentrated in autumn, particularly where fallen leaves pile up and stay damp. If your symptoms spike after raking leaves or walking through a wet, wooded area, mold is a likely contributor on top of whatever pollen is still circulating.
Indoor Allergens Shift With the Seasons Too
Your home isn’t a sealed bubble. Grass pollen levels inside houses spike sharply in May or June and drop back to baseline within about two months. Dust mite allergens follow a different pattern: they start climbing in July, roughly a month after indoor humidity rises, and stay elevated from August through December. These indoor fluctuations can be dramatic, with allergen levels varying more than twentyfold between peak and low months. So even if you stay inside, seasonal changes in what’s floating around your house still affect you.
Allergies or a Cold?
Seasonal allergies and the common cold share a lot of symptoms: sneezing, congestion, runny nose, fatigue. Two differences help you tell them apart. First, itchy eyes are a hallmark of allergies and rarely show up with a cold. Second, a fever points toward a virus, not allergies. If your symptoms last longer than 10 days without improving, or if they follow a predictable calendar pattern year after year, you’re almost certainly dealing with allergies.
Allergy Seasons Are Getting Longer
If it feels like your symptoms start earlier and last longer than they used to, you’re not imagining it. Rising temperatures are shifting pollen calendars. A long-term study spanning 27 years found that warming extended the pollen season for some plant species by nearly three months. For every 1°C increase in average temperature during spring, peak bloom shifted five to seven days earlier. Some plants with longer reproductive cycles could begin pollinating 20 to 30 days earlier in coming decades. The practical result: more days per year with pollen in the air and a longer window of misery for allergy sufferers.
When Pollen Counts Are Highest
The old advice to stay inside in the early morning turns out to be slightly off. Research tracking airborne pollen concentrations found that the lowest levels occur between 4 a.m. and noon. Pollen rises gradually after that and peaks between 2 p.m. and 9 p.m. If you’re planning outdoor exercise or yard work, morning is genuinely the better window.
Reducing Your Exposure
Checking your local pollen forecast before heading out is the simplest first step. Most weather apps and sites now include pollen counts broken down by type. Beyond that, a few changes make a real difference.
Keep windows closed during peak pollen hours in the afternoon and evening. Shower and change clothes after spending time outdoors, since pollen clings to hair, skin, and fabric. Running a HEPA filter indoors removes at least 99.97% of airborne pollen, mold spores, and dust particles, according to EPA testing standards. Placing one in your bedroom can significantly cut overnight exposure, which helps you wake up with fewer symptoms.
For dust mites, which peak in late summer and fall, washing bedding weekly in hot water and keeping indoor humidity below 50% limits their growth. If your symptoms span multiple seasons or don’t respond well to over-the-counter antihistamines, allergy testing can identify your specific triggers and open the door to more targeted treatment like immunotherapy.