How Long Does Pollen Season Last?

When most people say "pollen season," they mean the weeks in spring when their eyes itch and their nose runs. But there is no single pollen season. There are three overlapping ones, each driven by a different group of plants, and together they cover roughly ten months of the year.

Tree pollen comes first, starting as early as February in the South and running through May. Grass pollen follows from May through July. Weed pollen (ragweed above all) takes over from August through November. The only truly pollen-free months in most of the US are December and January, and even those are not guaranteed in the warmest states.

Pollen Season Calendar

Timing shifts by region. Southern states start earlier and end later. Northern states have a compressed but more intense season.

Tree Pollen: February through May

Tree pollen season is what most people think of as "allergy season." Trees pollinate before they fully leaf out, which is why spring allergies start before it even feels like spring. Oak, birch, cedar, and alder are the biggest producers, and a single oak tree can release tens of thousands of pollen grains per day.

In Atlanta, GA and other southern cities, tree pollen starts in mid-February and peaks in March and early April. In the Northeast, including New York, NY, the season starts in late March and peaks in late April through May. For a deeper look at spring tree pollen, see our Spring Pollen Season Guide.

Grass Pollen: May through July

Grass pollen picks up as tree pollen winds down, creating an overlap in May that makes that month miserable for many allergy sufferers. Bermuda grass, Timothy grass, and ryegrass are the main offenders. Grass pollen peaks in late May and June across most of the country.

Unlike tree pollen, which varies heavily by species and geography, grass pollen is fairly consistent across regions. If you are allergic to one type of grass pollen, you are likely reactive to most of them. Grass pollen season is shorter than tree season but can feel more intense because grass pollen grains are particularly good at triggering immune responses.

Weed Pollen: August through November

Ragweed dominates the fall pollen season. A single ragweed plant can produce up to one billion pollen grains over its lifetime, and that pollen can travel hundreds of miles on the wind. Ragweed season starts in mid-August and peaks in September and October across most of the US.

The season ends with the first hard frost. In northern states, that can be as early as mid-October. In Houston, TX and other Gulf Coast cities, ragweed can persist into November or even December. Mugwort, sagebrush, and pigweed also contribute to fall pollen counts, though ragweed does the heavy lifting.

How Timing Varies by Region

• South (GA, TX, FL, LA): Tree pollen starts as early as February. Grass pollen extends into August. Ragweed runs into November. Pollen activity can span 10+ months.
• Northeast (NY, MA, PA, CT): Tree pollen peaks April through May. Grass pollen peaks June. Ragweed runs September through mid-October. The overall season is compressed but intense.
• Midwest (IL, OH, MN, MO): Similar to the Northeast but with more ragweed. Fall weed pollen is often the worst season here.
• West (CA, OR, WA): Tree pollen starts early and can overlap with grass pollen in Los Angeles, CA. The Pacific Northwest has a long, moderate tree pollen season. Ragweed is less of a factor west of the Rockies.

Why Some People Suffer Year-Round

If you are allergic to more than one type of pollen, your symptoms may never fully stop. Someone allergic to both tree and grass pollen faces continuous exposure from February through July. Add a ragweed allergy and you are covered from February through November. Indoor allergens (dust mites, mold, pet dander) fill in the December and January gap. For year-round sufferers, daily pollen tracking becomes especially valuable for identifying which days are worse than others and adjusting medication timing accordingly.

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