Summer Pollen Season: What Allergy Sufferers Need to Know

Why Summer Is Grass Pollen Season

Grasses release pollen once the days grow long and daytime temperatures stay warm. That lines up with late spring and summer. Trees finish in a few weeks, but grasses keep pollinating for two to three months, so summer allergies tend to drag on longer than the spring kind.

Of the hundreds of grass species in North America, only about a dozen produce the pollen that sets off allergies. The pollen itself is light and dry, built to ride the wind for miles. Grass pollen is also one of the most potent asthma triggers worldwide, which is why a High grass day can leave you wheezing, not just sneezing.

There is a twist that spring does not have: you cut grass on purpose. Every time you mow, you fling pollen and mold spores straight into your breathing zone. A warm winter and a wet spring often mean a thicker, longer grass season, and warming temperatures have stretched North American pollen seasons about 20 days longer since 1990.

Grasses That Cause the Most Allergy Symptoms

A few grass species do most of the damage. Cool-season grasses like Timothy and Kentucky bluegrass rule the North. Warm-season grasses like Bermuda and Johnson grass take over the South and Great Plains. Here are the main culprits tracked by MyPollenPal:

Bermuda grass is the one to watch if you live in a warm climate. It pollinates for months instead of weeks, and in Florida and South Texas it can keep going into fall. In the Great Plains, June grass counts are often the highest of the whole year.

When Does Summer Pollen Season Start (and End)?

Grass pollen does not switch on everywhere at once. The timing shifts by region, and warm-season grasses in the South run far longer than the cool-season grasses up north:

• Southern states (Texas, Georgia, Florida, the Carolinas): Bermuda grass starts as early as April and can run into September. In Florida and South Texas, warm-season grasses pollinate for much of the year.
• Great Plains (Oklahoma, Kansas, Nebraska): Grass counts peak May through July and are often the highest in the country. Johnson grass adds a second wave in mid-summer.
• Midwest and Northeast (Illinois, Ohio, New York, Pennsylvania): Timothy and Kentucky bluegrass peak late May through July, then taper off in August.
• Pacific Northwest (Oregon, Washington): Ryegrass and orchard grass drive a strong May-through-July season. The Willamette Valley grows grass seed commercially, so counts there run high.

By the middle of August, grass fades and ragweed takes over as the main allergen across most of the country. If your symptoms keep going past Labor Day, weed pollen is the likely suspect, not grass.

Summer Allergies vs. a Summer Cold

A summer cold and grass allergies feel a lot alike at first. The difference is in how long they last and what sets them off. Here is how to tell them apart:

If your symptoms flare every June, last for weeks, and spike right after you cut the grass, that is almost certainly pollen. Checking your local pollen count can confirm it.

Grass pollen causes the full range of allergy symptoms. For a deeper look at specific reactions: why pollen makes you sneeze, pollen-related coughing, and chest tightness from allergic asthma.

Heat, Smog, and Thunderstorms

Summer piles on triggers that spring does not have. Grass pollen is the headliner, but three summer conditions can make a bad allergy day worse.

Ground-level ozone

Hot, sunny afternoons in cities push ground-level ozone up. Ozone is the main ingredient in summer smog, and it irritates airways that are already inflamed by pollen. It usually peaks in the afternoon and is lowest in the morning, so an early run beats an evening one on a hot day. Check today's conditions in your city before you plan outdoor exercise.

Thunderstorm asthma

A summer thunderstorm during grass season can trigger sudden asthma attacks, even in people who normally only get a stuffy nose. Strong downdrafts sweep pollen to ground level and high humidity ruptures the grains, releasing tiny particles small enough to reach deep into the lungs. If a storm is rolling in on a High grass day, stay inside with the windows shut until it passes.

Summer mold

Warm, humid weather and freshly cut grass feed outdoor mold spores, another trigger that overlaps with grass pollen. Mold counts climb after summer rain and in the hours after mowing. If your symptoms do not track the grass forecast, mold may be the missing piece.

One firm rule: trouble breathing is not something to wait out. Wheezing or shortness of breath means get medical care now, not a different antihistamine.

How to Manage Summer Grass Allergies

You cannot avoid grass pollen entirely, but you can cut your exposure and treat symptoms before they get bad. Here is what works:

Track pollen levels daily

Grass counts swing from day to day with heat, wind, and rain. Knowing whether today is a High or Low grass day helps you decide when to take medication, whether to exercise outdoors, and whether to keep the windows open. Check your city's pollen levels on MyPollenPal.

Rethink how you mow

Mowing is the fastest way to breathe in a cloud of grass pollen. If you have to do it yourself, wear an N95 mask, mow in the late afternoon when counts are dropping, and shower and change clothes as soon as you come in. If someone in the house does not react to grass, hand them the mower.

Start antihistamines early

Antihistamines work best before symptoms start. If grass pollen affects you every summer, begin a week or two before your region's season kicks off. Daily options like cetirizine (Zyrtec) or loratadine (Claritin) work best when you take them consistently.

Reduce indoor pollen exposure

• Run the air conditioner instead of opening windows on High and Very High grass days
• Shower and change clothes after time outdoors, and always after yard work
• Run a HEPA air purifier in your bedroom
• Dry laundry in a dryer, not on an outdoor line where pollen settles

Time your outdoor activity

Grass pollen tends to peak from midday into the early afternoon, a little later than tree pollen. Early morning after the dew, or the hour or two right after rain, are usually the cleanest windows. Check your best time of day to go outside for the full daily curve.

Use nasal sprays for congestion

Steroid nasal sprays like fluticasone (Flonase) calm the inflammation that antihistamines alone may not reach. They take a few days to build up, so start before your season, not after your nose is already blocked.

Ask about longer-term treatment

If an over-the-counter antihistamine has not helped after two weeks, or your grass allergy follows the same pattern every summer, see an allergist. Allergy shots and FDA-approved sublingual grass tablets can retrain your immune system over three to five years, and grass is one of the allergens these treatments target best.

What Pollen Levels Mean for Your Symptoms

MyPollenPal rates pollen severity on a scale from None to Very High. Here is what each level typically means for allergy sufferers:

Check Summer Pollen Levels in Your City

Grass pollen varies wildly from city to city. A High grass day in Oklahoma City does not mean Seattle is also High. The only way to know what is happening where you live is to check your local data.

Here are the cities where summer grass pollen hits hardest:

Browse all cities or search by ZIP code to find your local pollen report.

Want to see which cities are getting hit the hardest right now? Check today's worst pollen cities.

Sources

• American College of Allergy, Asthma & Immunology (ACAAI). "Grass Allergy." acaai.org
• Asthma and Allergy Foundation of America (AAFA). "Seasonal Allergies (Rhinitis)." aafa.org
• American Academy of Allergy, Asthma & Immunology (AAAAI). "Thunderstorm Asthma." aaaai.org
• American Academy of Allergy, Asthma & Immunology (AAAAI). "Allergen Immunotherapy." aaaai.org
• Anderegg WRL, Abatzoglou JT, Anderegg LDL, Meyerson LA, Levy A, Hicke JA. "Anthropogenic climate change is worsening North American pollen seasons." Proc Natl Acad Sci USA. 2021;118(7):e2013284118. doi:10.1073/pnas.2013284118

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