Worst Cities for Allergies (Seasonal Pollen-Load Ranking)

This is the always-current view of the ranking. For the named, dated edition — with the top-20 list, a season-onset map, a ZIP lookup, and per-metro quotable lines — see the WeatherStory Allergy Index 2026.

Which U.S. cities carry the heaviest pollen load across a full year? This ranking answers that with a single deterministic model: for each of the 100 largest U.S. cities by population, it scores modeled tree, grass, and ragweed intensity against how long each season lasts, then adds the three together into one pollen-load index. The 50 cities with the highest index are listed below, worst first.

The idea is not new. The Asthma and Allergy Foundation of America (AAFA) has published its annual Allergy Capitals report — a ranking of the 100 most-populous U.S. metro areas — for years, and the press cites it every spring. This page is modeled after that concept but built from a transparent, always-current seasonal model rather than a proprietary yearly score.

The 50 highest pollen-load U.S. cities

Peak columns show each allergen’s worst-month intensity on the None–Very High (0–4) seasonal scale. Season is the number of months with any active pollen. Load index = the sum of (peak × season length) for tree, grass, and ragweed — higher means a heavier, longer combined season.

How the pollen-load index is built

Every city is assigned a climate region from one of 9 zones, and its tree and grass seasons are shifted by latitude — Hopkins' bioclimatic law puts phenological events about 4 days later per degree north, so a northern city and a southern one in the same region do not score identically. That produces a 12-month intensity curve for each pollen type on a 0 to 4 scale, from None to Very High.

For each type we take the peak month's intensity and multiply it by the number of months that type stays in season. Tree, grass, and ragweed are summed into the composite index: a city scores high when it runs strong peaks across all three allergens and holds them for many months. In this run, Miami, FL tops the list at a load index of 54, with roughly 12 months of the year carrying active pollen. The 50th-ranked city, Reno, NV, scores 34.

Why this is not the AAFA Allergy Capitals score

AAFA's ranking weights three things: pollen scores, over-the-counter allergy-medicine use, and the availability of board-certified allergists in each metro. This page computes only the first of those, and it does so from a seasonal phenology model rather than measured daily counts. It cannot see how many people buy antihistamines or how hard it is to book an allergist, and it does not try to. Read it as a seasonal pollen-load ranking, not as a copy of AAFA's number.

That narrower scope is also its strength: because the index is a published formula built from regional season windows, anyone can trace why a city lands where it does. It is a model, not a measurement — the intensity values are drawn from AAFA and ACAAI regional season guidance, not from a pollen-counting station in each city.

What the ranking does and doesn't tell you

The heaviest loads cluster where warm, long growing seasons stack tree, grass, and ragweed on top of one another — the humid Southeast and the ragweed-heavy Plains run longer, more overlapping seasons than the mild West Coast or the short Alaskan calendar. Because the model has 9 regions plus a latitude shift, cities in the same region and near the same latitude can tie; the table breaks those ties by season area and population so the order stays stable, but small rank gaps between neighbors are not meaningful precision.

Use it as a starting point, not a diagnosis. Local tree cover, your specific sensitivities, and a given year's weather all matter, and no citywide number predicts how you personally will feel on a given morning. If seasonal symptoms disrupt your sleep or daily life, an allergist can test for your specific triggers. For the day-to-day picture, open your city's page below — each links to its tree, grass, and ragweed season calendar.

Pollen & allergy guides

Evergreen guides to what drives these seasons and how to manage them:

• Ragweed Allergy: Season, Symptoms, and Where It's Worst
• Hay Fever (Allergic Rhinitis): Causes, Seasons, and Relief
• Pollen Allergy Relief: What Actually Works
• Grass Pollen Allergy: Season, Triggers, and Relief
• Tree Pollen Allergy: Season by Region and the Worst Trees
• Pollen Count Scale: What Low, Moderate, High, and Very High Mean
• Allergy Season Calendar: When Each Pollen Peaks by Region
• Cedar Fever: Texas Mountain Cedar Season, Symptoms, and Relief
• Thunderstorm Asthma: How Storms Trigger Sudden Allergy Attacks
• Oral Allergy Syndrome: Why Pollen Makes Certain Foods Itch
• Mold Allergy: Outdoor Spore Season, Symptoms, and Relief
• Allergies vs. a Cold: How to Tell the Difference
• Allergy Immunotherapy: Shots, Tablets, and Long-Term Relief
• Allergy Testing: Skin Prick, Blood Tests, and What Results Mean
• Kids' Allergies: When They Start, Symptoms, and Safe Relief
• Winter Allergies: Indoor Triggers, Symptoms, and Relief
• Fall Allergies: What Triggers Them and When They Peak
• Dust Mite Allergy: Symptoms, Triggers, and How to Reduce Exposure
• Pine Pollen: Why the Yellow Dust Isn't Your Real Allergy Trigger
• Pollen Calendar: When Tree, Grass, Weed, and Mold Seasons Start and End
• Natural Allergy Remedies: What the Evidence Actually Shows
• Pet Allergies: Dander, Symptoms, and What Actually Reduces Exposure

More pollen data

Browse pollen counts by city for the full per-city tree, grass, and ragweed calendars, or see the national weather & climate rankings.