When Does Allergy Season Start

Key Takeaways

• Tree pollen usually starts in late winter to early spring across much of the U.S., triggering spring allergy symptoms for many people.

• Peak tree pollen most often falls between March and May, though southern areas may begin earlier, sometimes in February.

• Grass pollen tends to increase in late spring and into early summer after tree pollen declines.

• Warmer winters and early springs can bring the season on sooner and stretch it out.

• Begin preventive steps — medication, closing windows, using HEPA filters — about two weeks before your area’s typical start.

When Allergy Season Begins by Region

So when does allergy season kick off around the country? Regional timing varies: for much of the U.S., tree pollen begins in late winter to early spring and often peaks March through May, driving the primary spring allergy period. Southern and milder climates may see tree pollen as early as February or nearly year‑round, while northern zones have a later, shorter season. Grass pollen usually rises in late spring to early summer after tree pollen fades. In the Great Lakes and Midwest, heavy tree pollen fuels strong spring symptoms, and mold spores become more relevant later in the season. Because climate trends can advance or extend these phases, checking local forecasts is the best way to stay prepared.

Which Plants Trigger Early-Season Allergies

Which plants spark early-season allergies? In many parts of the U.S., tree pollen starts the season, often in late winter and peaking March–May. Common offenders include oak pollen, birch pollen, maple and alder — their windborne (anemophilous) grains travel far before grasses begin to pollinate. Tree pollen is microscopic and can drift miles, so you may get symptoms even when trees aren’t obvious nearby. Local vegetation and yearly weather change timing, so pollen counts are the best measure of exposure risk. Generally, trees dominate spring pollen and grasses follow later; watching forecasts helps pinpoint oak and birch peaks and the right time to act.

How Weather and Climate Shift Pollen Timelines

Weather and climate affect both when pollen appears and how much is in the air. Warmer temperatures and milder winters can bring pollen release forward, moving pollen season onset earlier and lengthening exposure for tree and grass pollen. Climate change tends to extend flowering periods, shifting peaks and increasing total pollen loads. Short‑term weather — heat, drought, humidity and rain — changes daily counts: rain can temporarily clear the air but may be followed by sharp post‑storm spikes, and wind carries pollen long distances. Local plants and regional climate interact, so impacts vary by area; keep an eye on local forecasts and pollen counts to anticipate changes and plan mitigation.

Recognizing the First Signs of Seasonal Allergies

How do you know seasonal allergies are starting? Early signs usually match tree pollen release in early spring. Common symptoms include sneezing, itchy or watery eyes, nasal congestion and a runny nose as oak, birch and maple pollen increase. Many people notice the same pattern each year, often after windy days or during morning hours when pollen is highest. Local climate shifts can move the season’s start earlier or later.

Preparing and Treating Ahead of Allergy Season

When should you start preparing to reduce seasonal allergy impact? Begin about two weeks before the typical start of tree pollen in your area. Use local pollen forecasts to time preventive treatment so daily medications begin before symptoms. Your plan might include starting prescribed or OTC nasal sprays and oral antihistamines as directed by a healthcare provider, plus practical steps: keep windows closed on high‑count days, run a HEPA‑filtered purifier indoors, and shower and change clothes after outdoor time to avoid bringing pollen inside. For many people this combination reduces symptoms and lowers overall medication needs; talk with your clinician to tailor timing and choose the right treatments for your health and local pollen patterns.