Pollen Calendar by Month and Region: When Allergy Season Starts Where You Live

How a Typical Pollen Year Works

Pollen allergy, also called hay fever or seasonal allergic rhinitis, comes in three broad waves. The Asthma and Allergy Foundation of America (AAFA) gives this general pattern (AAFA):

• Trees: February to April. Tree pollen is responsible for most spring pollen allergy symptoms. Common culprits include oak, birch, maple, elm, ash, cedar and juniper.
• Grasses: April to early June. Grasses cause most late-spring and summer symptoms, and their season often overlaps with the end of tree season.
• Weeds: August to the first hard frost. Ragweed is the best-known weed, but sagebrush, pigweed, lamb’s-quarters and Russian thistle can also cause symptoms.

That is the national average. Researchers at the University of Washington who built pollen calendars from 31 National Allergy Bureau stations found that start dates for tree and grass pollen depend strongly on latitude: the farther south you are, the earlier the season starts, and earlier starts go along with longer seasons (Lo et al., 2019). Average oak season length ranged from 23 days in Seattle to 103 days in San Jose, California (Lo et al., 2019). Not sure which group you react to? Allergy testing can show which pollens are your triggers.

Pollen Calendar by Month

Use this table as a starting point. Local timing varies with weather from year to year, and pollen forecasts can help you prepare, though you may still feel symptoms on days the forecast says pollen is low or moderate (AAFA).

Pollen Seasons by Region

The month-by-month pattern changes a lot from one part of the country to another. Here is how it plays out in several regions, based on long-term station data and regional experts.

Florida and the Southeast

Trees dominate in Florida, accounting for about 80% of the airborne pollen in the state, with oak the major player. February to May is peak season for Florida’s oaks, though some areas see high pollen counts as early as December, and Florida trees often release pollen from January to June (UF/IFAS). The yellow film of pine pollen on cars is hard to miss, but UF/IFAS notes that pine pollen is low-allergenic; more likely triggers include oak, eastern red cedar, bald cypress, wax myrtle and Australian pine (UF/IFAS). Grass pollen can be present year-round across the South (AAFA). For details, see when allergy season starts in Florida, our Florida oak pollen guide, pine and wax myrtle pollen and local Florida pollen forecasts.

Texas and the South Central States

Warm parts of the Great Plains have pollen in the air all year. At the Waco, Texas, station, researchers found three peaks: cedar and juniper in January, oak with hickory, maple and elm between late March and late April, and ragweed with other weeds from mid-September through October. Unlike northern stations, Waco’s lowest counts come in July (Lo et al., 2019). The winter peak is mountain cedar, or Ashe juniper. Texas A&M Forest Service says these trees typically begin producing pollen in mid-December, often after a cold front, peak in mid-January and taper off toward early March. Cedar fever is especially irritating in the Hill Country west of I-35 (Texas A&M Forest Service). See Texas pollen by city.

The Northeast, Midwest and Great Lakes

Cold winters give northern states a shorter, more compressed season. At a long-running station in London, Ontario, in the Great Lakes region, the main pollen season runs from March through September. Tree season ends as grass season begins in late May, and ragweed has a distinct season from mid-August to mid-September (Lo et al., 2019). Farther east, average oak season does not start until May 2 in Rochester, New York (Lo et al., 2019). AAAAI notes that in many parts of the country, ragweed season now starts in early August and runs through October rather than mid-August through September (AAAAI). Read more in our fall allergies guide and ragweed treatment guide.

The Pacific Northwest

In Seattle’s cool, moist climate, evergreen trees dominate. Cypress-family trees (cedar and juniper) and alder make up about two-thirds of the pollen collected there. Seattle sees very little pollen after July, so its season is relatively short (Lo et al., 2019). West Coast stations, including Seattle, Eugene and San Jose, also tend to start oak season earlier than inland stations at the same latitude (Lo et al., 2019). See Washington pollen by city.

California

San Jose is one of the few monitoring stations that samples year-round, because pollen is in the air throughout the year there. Trees produced 94% of the pollen identified, led by elm and olive. Elm shows two peaks because some species pollinate in spring and others in late summer and early fall (Lo et al., 2019). Grass pollen can also be found year-round in California (AAFA). See California pollen by city.

Looking for your area? Browse pollen by state or pollen by city.

Why Pollen Seasons Are Getting Longer

If your allergy seasons feel longer than they used to, the data back you up. A 2021 study in the Proceedings of the National Academy of Sciences analyzed pollen records from 60 North American stations between 1990 and 2018. It found pollen seasons advancing and lengthening (by about 20 days) and a 21% increase in pollen concentrations, closely tied to warming temperatures. The authors estimated that human-caused climate change contributed about half of the trend in pollen season timing and length (PNAS, 2021). AAAAI’s ragweed guidance reflects the same shift, with fall symptoms now starting earlier and ending later in many areas (AAAAI).

How to Use a Pollen Calendar

If symptoms in December or January do not line up with any local pollen season, indoor triggers may be the cause. See dust mite allergy in winter and winter allergies vs. a cold.

When to See an Allergist

If your symptoms stretch across more than one season, or medicines are not keeping up, an allergist can test for specific pollens and talk with you about long-term options such as allergy shots or under-the-tongue tablets. Pollen timing also matters during allergy shots, since allergists may take rising pollen levels into account when increasing doses (Lo et al., 2019). Browse the Find an Allergist directory or the Florida allergist directory.

Written by: SeasonalAllergies.org Editorial Team (November 12, 2026)

This article is for general education and is not medical advice. Talk with your doctor or an allergist about your symptoms before starting, stopping or changing any treatment.

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