Live tree, grass and weed pollen data across the USA, updated daily. The US has one of the longest combined pollen seasons in the world, running from January in southern states to October in the north. This page tracks pollen levels for the 20 highest-allergy cities in America, ranked by today’s PollenIQ™ score. Enter your ZIP code below to check the pollen count in your area right now.
Highest Pollen Count Cities in the US Right Now
The highest pollen count in the US today is tracked across 20 cities selected from the AAFA 2026 Allergy Capitals report. Pollen seasons have shifted significantly over the past two decades. The season now starts 20 days earlier and runs 10 days longer than it did in 1990, according to research published in the Proceedings of the National Academy of Sciences. Every city in this list is ranked live by its PollenIQ™ score, a composite index combining tree, grass and weed pollen levels plus local air quality. Scores update daily. The city at the top of this list has the worst pollen conditions in the US right now.
Tree, Grass and Weed Pollen Count Across the United States
The US pollen season does not follow one calendar. It follows three, running simultaneously across different regions and different plant species. Tree pollen starts in January in Texas. Grass pollen runs through August in the Great Plains. Weed pollen peaks in September from Kansas to Maine. Understanding which type is active in your region today tells you more than any single combined reading.
Tree pollen count in the US
Tree pollen count in the US varies more by region than any other allergen type. In Texas, mountain cedar produces pollen at temperatures as low as 40 degrees Fahrenheit, triggering what locals call Cedar Fever as early as December. Oak pollen dominates seven southeastern states from February through April, with Georgia and Alabama recording some of the highest oak counts in the country.
The Pacific Northwest runs on a different calendar. Alder is the primary early-season tree allergen in Washington and Oregon, peaking in February before birch arrives in March. In California’s Central Valley, olive trees are a significant allergen that does not exist in the eastern half of the country at all. Tree pollen carries a 45% weight in the PollenIQ™ score, reflecting how consistently it dominates the first half of the allergy year across the US.
Weed pollen count by US region
Weed pollen count by US region splits the country in two. East of the Rockies, ragweed dominates. The ragweed belt covers Kansas, Nebraska, Iowa, and the broader Midwest and Eastern United States, where the highest concentrations in the country are recorded during peak weeks in August and September.
About 1 in 7 people in the US are allergic to ragweed pollen. West of the Rockies the picture changes completely. Seattle, Portland, and most of the Pacific Northwest have virtually no ragweed. Sagebrush takes over as the primary weed allergen across Nevada, Utah, and Wyoming. Mugwort is the dominant weed allergen in California. Ragweed season is also getting longer. EPA climate data shows the season has grown by 21 days in Fargo, North Dakota and 18 days in Minneapolis, Minnesota since 1995, driven by later first frost dates allowing ragweed to pollinate deeper into fall. In some northern locations the increase reaches 27 days.
Grass pollen count across America
Grass pollen count across America is highest in the Great Plains states. Kansas, Oklahoma, and Nebraska record some of the most intense grass pollen seasons in the country, driven by native prairie grasses that cover millions of acres with no natural break in coverage.
In Florida and Texas, Bermuda grass is perennial. It never fully stops producing pollen, giving southern states a near year-round grass problem while northern states get a clean break each winter. The Corn Belt adds a layer most people miss. Iowa, Illinois, and Indiana carry elevated grass pollen from agricultural crops through the summer months, compounding natural grass seasons.
Peak timing shifts by latitude. Timothy grass peaks in June in Minnesota and peaks in May in Tennessee. The same species, a month apart, because of a single degree difference in average spring temperatures across latitude.
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GET RELIEFWhen Is Pollen Season in the US?
Pollen season in the US does not have a single start date. It has three, staggered by region and plant type, running from January in the South to October in the North. In practice, the allergy year never fully stops for most Americans. One season ends and another begins within weeks.
Tree pollen opens the year. Southern states like Texas and Georgia see tree pollen as early as December and January. Northern states follow from March through May, with birch, oak, and maple as the primary triggers. By the time tree season winds down in the North, grass pollen is already peaking across the Great Plains and Midwest. Grass runs from May through August depending on latitude, with the longest seasons in Florida and Texas where warm-season grasses are active almost year-round.
Weed pollen closes the year. Ragweed starts releasing pollen in early August across most of the country and runs until the first hard frost, typically in October or November. Research published in PNAS found that the overall North American pollen season now starts 20 days earlier and lasts 8 days longer than it did in 1990, with total pollen concentrations 21% higher over the same period. For the 81 million Americans who suffer from seasonal allergies, that means more months of exposure, not just more pollen on bad days.
US States with the Highest Pollen Count
The states with the highest pollen count in the US are concentrated in two regions: the South and the Great Plains. Geography, climate, and vegetation combine to create conditions that produce more pollen, more intensely, and for longer than anywhere else in the country. Over 100 million Americans live with allergies, making it the sixth leading cause of chronic illness in the US, according to AAFA. In some parts of the country, pollen season never fully stops.
Texas leads the country in sheer pollen variety. Mountain cedar dominates winter, oak takes over in spring, Bermuda grass runs through summer, and ragweed closes the year. No other state runs all four major allergen types at significant levels across all four seasons. Georgia and Alabama follow closely, driven by one of the densest oak canopies in North America and a climate warm enough to extend both tree and grass seasons well beyond the national average.
The Great Plains states hit differently. Kansas, Oklahoma, and Nebraska do not have the species variety of the South, but what they have is scale. Native prairie grasses cover tens of millions of acres. When grass pollen season peaks across the Plains in June, there is no urban buffer, no tree canopy break, and no geographic barrier to stop pollen from spreading across state lines. Wichita, Kansas ranked as the number one Allergy Capital three years in a row from 2023 to 2025, driven by higher than average tree and grass pollen loads and limited access to allergy specialists, before Boise, Idaho took the top spot in 2026.
US States with the Lowest Pollen Count
The states with the lowest pollen count in the US share one characteristic more than any other: low humidity combined with limited dense vegetation. Dry air does not carry pollen as effectively as humid air, and sparse plant cover means less pollen production to begin with. For the roughly 100 million Americans who live with seasonal allergies, geography matters.
Nevada, Wyoming, Arizona, Colorado, and Montana consistently rank among the most allergy-friendly states in the country. These states have low levels of both pollen and ragweed driven by dry desert and high-altitude climates that limit the variety and density of pollen-producing plants. The Pacific Northwest presents a different case. Seattle and Portland have virtually no ragweed, which alone removes one of the most potent allergens from the equation for residents. Tree pollen is present in spring, but the overall allergen load is significantly lower than in the South or Great Plains.
Altitude plays a role that most people do not consider. States like Colorado and Wyoming sit at elevations where the growing season is shorter, hard frosts arrive earlier in autumn, and the number of days with high pollen output is reduced compared to lower-elevation states. Arizona’s sparse desert vegetation means fewer trees and grasses producing pollen, with the dry air further reducing the risk of allergen spread, making cities like Phoenix more manageable for allergy sufferers than their warm climate might suggest. That said, no US state is entirely pollen-free. Every region has at least one pollen season worth monitoring, which is why tracking your local PollenIQ™ score matters regardless of where you live.
Pollen Count USA: Your Questions Answered
Pollen count questions across the US follow predictable patterns. Whether you are tracking tree pollen in Atlanta, cedar pollen in San Antonio, or ragweed levels across the Midwest, the six questions below cover what allergy sufferers ask most about pollen tracking, the PollenIQ™ score, and how to read your hay fever forecast.
Questions about pollen counts and allergy seasons across the United States
The highest pollen count in the US shifts from city to city depending on the season and the allergen type. No single city holds the top spot year-round. According to the AAFA 2026 Allergy Capitals report, Boise, Idaho ranked as the number one city for pollen allergies in 2026, followed by San Diego, Tulsa, Provo, and Rochester. This was a significant shift from previous years when Wichita, Kansas held the top spot for three consecutive years.
For tree pollen specifically, Georgia consistently records some of the highest counts in the country. Atlanta pollen season is particularly intense in spring, driven by one of the densest oak canopies in North America. Atlanta records oak pollen counts that regularly exceed 1,500 grains per cubic meter on peak days in March and April. The allergy community refers to conditions like this as a pollen vortex, when multiple tree species release simultaneously during a warm spell after rain.
San Antonio’s cedar pollen is legendary among allergy sufferers. Mountain cedar pollen in San Antonio has been recorded at over 10,000 grains per cubic meter on extreme days in January and February, one of the highest single-allergen counts of any US city. Locals call the reaction Cedar Fever, and it affects millions of Texans each winter.
For grass pollen, the Great Plains states record the most intense seasons. Kansas and Nebraska carry high pollen loads from native prairie grasses covering tens of millions of acres. For ragweed, the Midwest and East consistently record the worst counts in August and September, with the ragweed belt running from the Plains through to the Northeast.
The PollenIQ tracker above this page ranks all 20 of the highest-allergy US cities by today’s live composite pollen index score, so you can see which city has the worst conditions right now. Weather conditions drive significant day-to-day variation. Warm, dry, and windy days push counts to their peaks. Rain and cold temporarily reduce them, often sharply.
Here are all six with inline citations embedded in the text, ready to copy-paste directly into GP:
Q1: Where is the highest pollen count in the US?
The highest pollen count in the US shifts from city to city depending on the season and the allergen type. No single city holds the top spot year-round. According to the AAFA 2026 Allergy Capitals report, Boise, Idaho ranked as the number one city for pollen allergies in 2026, followed by San Diego, Tulsa, Provo, and Rochester. This was a significant shift from previous years when Wichita, Kansas held the top spot for three consecutive years.
For tree pollen specifically, Georgia consistently records some of the highest counts in the country. Atlanta pollen season is particularly intense in spring, driven by one of the densest oak canopies in North America. Atlanta records oak pollen counts that regularly exceed 1,500 grains per cubic meter on peak days in March and April. The allergy community refers to conditions like this as a pollen vortex, when multiple tree species release simultaneously during a warm spell after rain.
San Antonio’s cedar pollen is legendary among allergy sufferers. Mountain cedar pollen in San Antonio has been recorded at over 10,000 grains per cubic meter on extreme days in January and February, one of the highest single-allergen counts of any US city. Locals call the reaction Cedar Fever, and it affects millions of Texans each winter.
For grass pollen, the Great Plains states record the most intense seasons. Kansas and Nebraska carry high pollen loads from native prairie grasses covering tens of millions of acres. For ragweed, the Midwest and East consistently record the worst counts in August and September, with the ragweed belt running from the Plains through to the Northeast.
The PollenIQ tracker above this page ranks all 20 of the highest-allergy US cities by today’s live composite pollen index score, so you can see which city has the worst conditions right now. Weather conditions drive significant day-to-day variation. Warm, dry, and windy days push counts to their peaks. Rain and cold temporarily reduce them, often sharply.
Q2: What month is pollen at its highest in the US?
Pollen is at its highest in the US in April and May for most of the country, but that answer changes depending on your region and which allergen type you react to. The US does not have one pollen peak. It has three staggered peaks across the calendar year that affect different regions at different times, and all three are getting worse.
Tree pollen peaks first. Across most of the country, tree pollen is at its highest from March through May. April is the worst month for most northern and midwestern states. In the Southeast, the peak arrives earlier. Georgia pollen counts routinely spike in late February and March when oak, birch, and maple release simultaneously. Atlanta pollen season can begin as early as January in warm winters. In Texas, cedar pollen peaks in January and February, making winter the worst allergy season for millions of Texans rather than spring.
Grass pollen takes over in late spring and runs through summer. June is typically the worst month for grass pollen across the Great Plains and Midwest, where native prairie grasses and agricultural crops combine to push counts to their annual high. In southern states like Florida and Texas, Bermuda grass is active much longer, with elevated grass pollen counts from May through September in some years.
Ragweed defines the fall allergy season. August and September are the worst months for ragweed pollen across the East and Midwest. A single ragweed plant produces up to one billion pollen grains per season, and it releases most of that between dawn and mid-morning on warm, dry, windy days. Ragweed pollen is light enough to travel 400 miles out to sea and two miles up in the atmosphere.
One factor often overlooked is mold. Mold spores follow a different calendar than pollen, peaking after heavy rain events and through late summer into autumn. People who experience allergy symptoms outside of traditional pollen months are often reacting to mold rather than tree, grass, or weed pollen.
Research published in PNAS found that pollen season across North America now starts 20 days earlier than it did in 1990 and produces 21% more pollen overall. For most Americans, April and May have become significantly worse over the past three decades.
The US states with the worst allergy season are concentrated in the South and the Great Plains. Texas, Georgia, Oklahoma, Kansas, and the broader southeastern states consistently appear at the top of allergy severity rankings, driven by a combination of climate, vegetation density, and the length of their pollen seasons.
Texas stands in a category of its own for overall annual allergen load. No other state runs four major allergen types at significant levels across all four seasons. Mountain cedar produces its famous cedar pollen from December through February, causing what locals call Cedar Fever in San Antonio and the Hill Country. Oak takes over in spring, Bermuda grass dominates summer, and ragweed closes out the year. For allergy sufferers in Texas, genuine relief is rare.
Georgia ranks among the worst states for tree pollen. Atlanta pollen season is particularly intense, driven by one of the densest oak canopies in North America. The city regularly records tree pollen counts that exceed levels classified as extremely high by the National Allergy Bureau. Georgia pollen counts during peak spring weeks are among the highest recorded in any US state.
The Great Plains states lead for grass pollen severity. Oklahoma has been identified as the worst state for outdoor allergies overall, with severity ratings near the top of the national scale for grass pollen, tree pollen, and ragweed combined. Kansas and Nebraska are close behind. The flat, open landscape offers no geographic barrier to pollen dispersal, allowing counts to build and spread across state lines during peak season.
The AAFA 2026 Allergy Capitals report found that western states made significant gains in the rankings due to wet weather in late 2024 that fed plant growth and produced higher than normal grass and weed pollen seasons in Idaho, Washington, and California. For the first time in the report’s history, the top spot went to a western city.
Allergy symptoms are shaped by more than state borders. Weather patterns, local vegetation, and urban tree canopy all affect how intense your personal season gets, which is why tracking your city-level pollen index daily gives more accurate information than state-level generalizations.
The best US states for allergy sufferers are generally found in the Mountain West and parts of the Pacific Northwest, where dry climates, high altitudes, and limited dense vegetation combine to reduce the variety and intensity of airborne allergens. Nevada, Wyoming, Colorado, Montana, and Utah consistently rank among the most allergy-friendly states in the country.
The defining factor is not temperature. It is humidity. Humid air carries pollen more effectively than dry air, and mold spores thrive in wet conditions. States with low humidity and arid or semi-arid climates naturally limit the airborne allergen load. Nevada’s desert landscape limits the variety of pollen-producing plants dramatically. Las Vegas records far lower tree pollen and grass pollen counts than comparably sized cities in the South or Midwest, despite being a warm city.
Altitude plays a role that most people do not consider. States like Colorado and Wyoming sit at elevations where growing seasons are shorter, hard frosts arrive earlier in autumn, and the total number of high-pollen days per year is reduced. Denver’s allergy season is shorter and less intense than cities at similar latitudes in the Midwest, partly because of altitude and partly because the surrounding landscape produces less pollen per square mile than Great Plains prairie states.
The Pacific Northwest presents a different case. Seattle and Portland have virtually no ragweed, which removes one of the most potent allergens entirely. Tree pollen is present in spring, primarily from alder and birch, but the total annual allergen load is significantly lower than in the South. The trade-off is mold. The wet climate produces elevated mold spore counts through autumn, which affect a different subset of allergy sufferers.
Utah is frequently cited as one of the best states for hay fever sufferers specifically. The high-altitude desert environment, dry air, and relatively low vegetation density make it more manageable than most states for people sensitive to grass pollen and tree pollen.
That said, no US state is entirely pollen-free. Even Nevada has olive, mulberry, and sagebrush producing pollen during their respective seasons. The most reliable approach is tracking the live pollen tracker score for your specific city across all three allergen types rather than relying on state-level rankings that average out significant local variation.
Pollen allergies are getting worse for a documented reason: climate change is making pollen seasons longer, more intense, and causing plants to produce more pollen per season. Research published in the Proceedings of the National Academy of Sciences found that the North American pollen season now starts 20 days earlier and lasts 8 days longer than it did in 1990, with total pollen concentrations 21% higher over the same period.
The mechanism is straightforward. Higher carbon dioxide levels in the atmosphere cause plants to produce more pollen. Warmer temperatures extend the period during which plants release pollen. Later first frost dates allow ragweed and weed pollen to keep releasing deep into autumn in regions where it used to stop in September. The result is more pollen in the air, for more months of the year, triggering allergy symptoms and hay fever reactions that were historically manageable for many people.
Weather is the most immediate driver of how bad allergies feel on any given day. Warm, dry, and windy conditions are the worst combination for allergy sufferers. Wind disperses pollen from its source over long distances. Tree pollen is light enough to travel hundreds of miles. A high-wind day during peak season can push pollen counts to extreme levels even in areas with relatively low local vegetation.
Rain temporarily washes pollen from the air and gives most allergy sufferers a break. But the relief is short-lived. Within hours of rain stopping on a warm day, pollen counts can spike sharply as plants release pollen in the calmer, warmer air that follows.
Urban areas have their own compounding problem. The AAFA notes that warmer urban temperatures create a heat island effect that stimulates additional pollen production from city trees. A 1949 US Department of Agriculture guideline recommended planting only male, wind-pollinating trees in cities, meaning many US urban areas carry unusually high pollen loads compared to natural environments. This is sometimes called botanical sexism, and its effects are still visible in the tree canopy of most major American cities.
There is also evidence that pollen is becoming more allergenic, not just more abundant. Elevated CO2 levels cause some plants to produce pollen that triggers stronger immune responses, meaning the same amount of pollen causes worse allergy symptoms than it did in previous decades.
Pollen season in the US does not have one end date. It has three, and they vary significantly by region and allergen type. For most Americans, some type of pollen is active from January through October. In southern states, the allergy year runs almost continuously.
Tree pollen season ends first. In most northern states, tree pollen wraps up by late May or early June as birch, oak, and maple complete their pollination cycles. In the South, tree season can extend into June in warm years. In Texas, mountain cedar is a winter allergen that peaks in January and February, so cedar allergy sufferers get their relief in March, while those reacting to oak continue through spring.
Grass pollen season ends in late summer. In most of the country, grass pollen drops significantly by August as many grass species complete their pollination cycle. In northern states, grass season often ends by late July. In southern states like Florida and Texas, warm-season grasses are active much longer, with Bermuda grass producing pollen into September or later in warm years.
Ragweed defines how late the allergy year runs. Ragweed season ends with the first hard frost, which arrives in October across most northern states and as late as November in the South. EPA climate data shows the ragweed season has grown by 21 days in Fargo, North Dakota and 18 days in Minneapolis, Minnesota since 1995, driven by later frost dates. In some northern locations the increase reaches 27 days.
For most Americans outside the deep South and Texas, the allergy year effectively ends after the first hard frost in October. For residents of Florida, southern Texas, and southern California, some level of grass pollen and weed pollen activity continues into November and December. The AAFA notes that some parts of the US now experience pollen year-round.
Tracking the PollenIQ score for your city through autumn tells you exactly when your local season ends, rather than relying on national averages. When the score drops to Very Low for several consecutive days following a frost event, pollen season in your area has effectively ended until the following spring.