What is the WeatherStory Allergy Index?

It is a modeled seasonal pollen-load ranking of the 100 largest U.S. metropolitan areas. For each metro it scores modeled tree, grass, and ragweed intensity against how long each season lasts, then sums the three into one load index. It is inspired by AAFA's long-running Allergy Capitals report but built from a transparent, always-current seasonal model rather than a proprietary yearly score.

Is this the same as AAFA's Allergy Capitals?

No. AAFA's Allergy Capitals report also weights over-the-counter allergy-medicine use and the number of board-certified allergists in each metro. The WeatherStory Allergy Index computes only modeled seasonal pollen load, from regional season windows and each city's latitude rather than measured daily counts. Read it as a related but different, transparently reproducible ranking — not a copy of AAFA's number.

Which U.S. metro ranks #1 in 2026?

Miami, Florida tops the 2026 index with a seasonal load index of 54. Its worst allergen is grass, whose season runs about 365 days, and its overall active-pollen window spans roughly 365 days a year.

How long is the typical pollen season?

Across the 100 ranked metros, the median active-pollen window — any of tree, grass, or ragweed at Low or above — is about 274 days, and 13 metros run a near-year-round season of 330+ days. Warm, humid metros that stack tree, grass, and ragweed back to back carry the longest seasons; short, cold, or dry climates carry the shortest.

How accurate is the ranking?

It is a model, not a measurement. The intensity values come from published regional season windows (AAFA/ACAAI) shifted by latitude (Hopkins' bioclimatic law), not from a pollen-counting station in each city, so treat small rank gaps between neighbors as noise, not precision. The value is transparency: the formula is published on the methodology page, so anyone can trace why a metro lands where it does.

Can I republish the ranking?

Yes — with attribution. Please credit "WeatherStory Allergy Index 2026, edition 2026.2 (weatherstory.io/allergy-index/2026)" and link the methodology page. A recommended citation line is provided at the bottom of this report. Quote the edition number too: the ranking is recomputed when the model changes, and the 2026.1 run had a different #1.

WeatherStory Allergy Index 2026

Name: WeatherStory Allergy Index 2026
Published: 2026-07-11
License: https://weatherstory.io/methodology

Edition 2026.2 · revised 2026-09-16 · what changed

The 100 largest U.S. metros, ranked by a modeled seasonal pollen-load index — tree, grass, and ragweed intensity multiplied by season length. Miami, FL leads with a load index of 54. A transparent, always-current alternative to static “allergy capitals” lists.

Top 20 worst U.S. metros for allergies (2026)

The 20 highest pollen-load U.S. metros

Each dot is a top-20 metro, shaded by its pollen-load rank (darkest = worst). The top 10 are labeled; contiguous U.S. plus the Alaska and Hawaii insets — Puerto Rico is ranked in the table but is outside this projection.

Source: WeatherStory Allergy Index 2026 — a modeled seasonal pollen-load ranking, not measured counts. See methodology.

How the index is built

Every metro is assigned one of nine U.S. climate regions, and its tree and grass seasons are shifted by latitude — Hopkins’ bioclimatic law puts phenological events roughly four days later per degree north, which moves a season’s start and endwithout changing its length. That yields a 12-month intensity curve (0–4, from None to Very High) for each pollen type. We multiply each type’s peak intensity by the number of months it stays in season and sum tree, grass, and ragweed into the load index. This is a modeled seasonal pollen-load ranking — not a copy of AAFA’s proprietary Allergy Capitals score (which also weights over-the-counter medication use and allergist density), and not measured pollen counts. AAFA established the ranked-annual-report concept; this is a transparent, reproducible take on it. Full formula, thresholds, and sources: methodology.

One allergen sits outside that three-wave calendar. In the Central Texas Hill Country, mountain cedar (Ashe juniper, Juniperus ashei) pollinates from mid-December through February, peaking in mid-January — the reaction known as cedar fever. Edition 2026.2 adds that winter lobe to the tree curve for metros inside the Edwards Plateau belt (roughly 29.0–32.2°N, 101.5–96.8°W, in Texas), which is why Austin and San Antonio now carry a January pollen season. Dallas, Fort Worth and Oklahoma City are left unchanged: they get cedar pollen carried in on winter cold fronts, which is an episodic transport event rather than a local season. See the cedar fever guide.

What changed in 2026.2

Edition 2026.1 (published 2026-07-11) applied Hopkins’ latitude shift as a widening of each season’s edges: any city more than about three-quarters of a degree from its region’s anchor metro picked up an extra month at each end, so modeled seasons got longer the farther a city sat from its anchor. Hopkins’ law says a phenological event happens about four days later per degree of latitude north — it moves a season, it does not lengthen one. Edition 2026.2, computed 2026-09-16, applies the shift to the season’s start and end, and counts a calendar month as in season only when the shifted season covers at least half of it.

The correction shortened seasons and re-ranked the table. Under 2026.1 the #1 metro was Cape Coral, FL and the median active-pollen window across the 100 metros was 304 days; under 2026.2 the #1 metro is Miami, FL and the median is 274 days. The same revision added the mountain-cedar season described above, which is why two Texas metros move up sharply. Numbers quoted from the earlier run are not wrong citations — they are 2026.1 numbers, and this page is 2026.2.

What is a high pollen count?

A pollen count is measured in grains per cubic meter of air (grains/m³), averaged over 24 hours, and rated by the AAAAI National Allergy Bureau (NAB) on a Low → Very High scale. The thresholds differ by pollen type: grass counts as “High” at just 20 grains/m³, while tree pollen isn’t “High” until 90.

NAB pollen-count categories, grains/m³ (by pollen type)
Category	Tree	Grass	Weed (ragweed)
Low	0–14	0–4	0–9
Moderate	15–89	5–19	10–49
High	90–1,499	20–199	50–499
Very High	1,500+	200+	500+

Those grains/m³ categories describe a single day’s measured count. The WeatherStory Allergy Index above is a different measure — a modeled seasonal load score that multiplies each pollen type’s peak intensity by how long its season runs, so it ranks metros over a whole year rather than one day. For the full per-type ranges and the separate 0–12 pollen index, see the pollen & allergy statistics hub.

When does allergy season start?

As of September 2026, spring tree pollen has finished across most of the Lower 48, grass pollen is past its typical May–July peak (it runs longer in the South and West), and ragweed — the dominant fall allergen — is in its typical August–October peak season, which ends at the first hard freeze (about 28°F).

Allergy season starts earlier the farther south and west you live. The map colors each state by the typical first month of the year with active pollen among its ranked metros — as early as January in the warmest states. Enter your ZIP to see your nearest ranked metro’s onset month, worst allergen, and rank.

Source: WeatherStory Allergy Index 2026, modal season-onset month per state. A modeled estimate — see methodology.

Pollen season calendar: when tree, grass & ragweed peak

Three pollen types hand off across the year in the same order almost everywhere in the U.S. — trees first, then grasses, then ragweed — each shifted earlier the farther south you live.

Allergen	Season	Peak months
Tree	Late winter to late spring	March–May (as early as December–February in the warm South)
Grass	Late spring through summer	May–July (longer and later in the South and West)
Ragweed (weed)	Late summer through fall	August–October, ending at the first hard freeze (about 28°F)

Windows are typical U.S. ranges (AAFA / ACAAI); local start dates shift with latitude and the year’s weather.

Quotable lines for the top 10 metros

One ready-to-cite sentence per metro. Copy with attribution to “WeatherStory Allergy Index 2026, edition 2026.2.”

Miami's grass pollen season runs 365 days, with a seasonal load index of 54 — #1 of 100 U.S. metros.
San Juan's grass pollen season runs 365 days, with a seasonal load index of 54 — #2 of 100 U.S. metros.
Cape Coral's grass pollen season runs 365 days, with a seasonal load index of 54 — #3 of 100 U.S. metros.
Bonita Springs's grass pollen season runs 365 days, with a seasonal load index of 54 — #4 of 100 U.S. metros.
Austin's tree pollen season runs 152 days, with a seasonal load index of 50 — #5 of 100 U.S. metros.
San Antonio's grass pollen season runs 183 days, with a seasonal load index of 46 — #6 of 100 U.S. metros.
Dallas's grass pollen season runs 183 days, with a seasonal load index of 42 — #7 of 100 U.S. metros.
Atlanta's grass pollen season runs 183 days, with a seasonal load index of 42 — #8 of 100 U.S. metros.
Tampa's grass pollen season runs 183 days, with a seasonal load index of 42 — #9 of 100 U.S. metros.
Indianapolis's grass pollen season runs 183 days, with a seasonal load index of 42 — #10 of 100 U.S. metros.

Full ranking: 100 U.S. metros

#	Metro	Worst allergen	Season starts	Season length	Load index
1	Miami, FL	Grass (year-round)	January	365 days	54
2	San Juan, PR	Grass (year-round)	January	365 days	54
3	Cape Coral, FL	Grass (year-round)	January	365 days	54
4	Bonita Springs, FL	Grass (year-round)	January	365 days	54
5	Austin, TX	Tree (Dec–Apr)	January	365 days	50
6	San Antonio, TX	Grass (Mar–Aug)	January	365 days	46
7	Dallas, TX	Grass (Apr–Sep)	February	304 days	42
8	Atlanta, GA	Grass (Apr–Sep)	February	304 days	42
9	Tampa, FL	Grass (Mar–Aug)	January	335 days	42
10	Indianapolis, IN	Grass (May–Oct)	March	274 days	42
11	Cincinnati, OH	Grass (May–Oct)	March	274 days	42
12	Kansas City, MO	Grass (May–Oct)	March	274 days	42
13	Columbus, OH	Grass (May–Oct)	March	274 days	42
14	Charlotte, NC	Grass (Apr–Sep)	February	304 days	42
15	Raleigh, NC	Grass (Apr–Sep)	February	304 days	42
16	Memphis, TN	Grass (Apr–Sep)	February	304 days	42
17	Oklahoma City, OK	Grass (Apr–Sep)	February	304 days	42
18	Fort Worth, TX	Grass (Apr–Sep)	February	304 days	42
19	McAllen, TX	Grass (Mar–Aug)	January	335 days	42
20	Charleston, SC	Grass (Apr–Sep)	February	304 days	42
21	Dayton, OH	Grass (May–Oct)	March	274 days	42
22	Knoxville, TN	Grass (Apr–Sep)	February	304 days	42
23	Palm Bay, FL	Grass (Mar–Aug)	January	335 days	42
24	Port St. Lucie, FL	Grass (Mar–Aug)	January	335 days	42
25	Kissimmee, FL	Grass (Mar–Aug)	January	335 days	42
26	Little Rock, AR	Grass (Apr–Sep)	February	304 days	42
27	Orlando, FL	Grass (Mar–Aug)	January	335 days	42
28	Nashville, TN	Grass (Apr–Sep)	February	304 days	42
29	Birmingham, AL	Grass (Apr–Sep)	February	304 days	42
30	Tulsa, OK	Grass (Apr–Sep)	February	304 days	42
31	Columbia, SC	Grass (Apr–Sep)	February	304 days	42
32	Denton, TX	Grass (Apr–Sep)	February	304 days	42
33	Houston, TX	Grass (Mar–Aug)	January	335 days	39
34	St. Louis, MO	Grass (May–Oct)	March	274 days	39
35	Virginia Beach, VA	Grass (Apr–Sep)	February	304 days	39
36	Jacksonville, FL	Grass (Apr–Sep)	February	304 days	39
37	Richmond, VA	Grass (May–Oct)	March	274 days	39
38	Louisville, KY	Grass (May–Oct)	March	274 days	39
39	New Orleans, LA	Grass (Apr–Sep)	February	304 days	39
40	Baton Rouge, LA	Grass (Apr–Sep)	February	304 days	39
41	Wichita, KS	Grass (May–Oct)	March	274 days	39
42	San Francisco, CA	Tree (Jan–Apr)	January	274 days	34
43	San Diego, CA	Tree (Jan–Apr)	January	274 days	34
44	Portland, OR	Grass (Apr–Jul)	February	274 days	34
45	Sacramento, CA	Tree (Feb–May)	February	274 days	34
46	San Jose, CA	Tree (Jan–Apr)	January	274 days	34
47	Fresno, CA	Tree (Jan–Apr)	January	274 days	34
48	Bakersfield, CA	Tree (Jan–Apr)	January	274 days	34
49	Concord, CA	Tree (Feb–May)	February	274 days	34
50	Reno, NV	Tree (Feb–May)	February	274 days	34
51	New York, NY	Tree (Mar–May)	March	244 days	30
52	Los Angeles, CA	Tree (Jan–Apr)	January	274 days	30
53	Seattle, WA	Tree (Feb–May)	February	274 days	30
54	Minneapolis, MN	Ragweed (Aug–Nov)	April	244 days	30
55	Brooklyn, NY	Tree (Mar–May)	March	244 days	30
56	Queens, NY	Tree (Mar–May)	March	244 days	30
57	Riverside, CA	Tree (Jan–Apr)	January	274 days	30
58	Manhattan, NY	Tree (Mar–May)	March	244 days	30
59	Omaha, NE	Ragweed (Aug–Nov)	March	274 days	30
60	Mission Viejo, CA	Tree (Jan–Apr)	January	274 days	30
61	Allentown, PA	Tree (Mar–May)	March	244 days	30
62	Des Moines, IA	Ragweed (Aug–Nov)	March	274 days	30
63	Staten Island, NY	Tree (Mar–May)	March	244 days	30
64	Long Beach, CA	Tree (Jan–Apr)	January	274 days	30
65	Chicago, IL	Tree (Mar–May)	March	244 days	30
66	Philadelphia, PA	Tree (Mar–May)	March	244 days	30
67	Washington, DC	Tree (Mar–May)	March	244 days	30
68	Boston, MA	Tree (Mar–May)	March	244 days	30
69	Detroit, MI	Tree (Mar–May)	March	244 days	30
70	Baltimore, MD	Tree (Mar–May)	March	244 days	30
71	Pittsburgh, PA	Tree (Mar–May)	March	244 days	30
72	Cleveland, OH	Tree (Mar–May)	March	244 days	30
73	Bronx, NY	Tree (Mar–May)	March	244 days	30
74	Providence, RI	Tree (Mar–May)	March	244 days	30
75	Milwaukee, WI	Tree (Mar–May)	March	244 days	30
76	Hartford, CT	Tree (Mar–May)	March	244 days	30
77	Bridgeport, CT	Tree (Mar–May)	March	244 days	30
78	Buffalo, NY	Tree (Mar–May)	March	244 days	30
79	Rochester, NY	Tree (Mar–May)	March	244 days	30
80	Grand Rapids, MI	Tree (Mar–May)	March	244 days	30
81	Albany, NY	Tree (Mar–May)	March	244 days	30
82	New Haven, CT	Tree (Mar–May)	March	244 days	30
83	Akron, OH	Tree (Mar–May)	March	244 days	30
84	Harrisburg, PA	Tree (Mar–May)	March	244 days	30
85	Worcester, MA	Tree (Mar–May)	March	244 days	30
86	Toledo, OH	Tree (Mar–May)	March	244 days	30
87	Madison, WI	Tree (Mar–May)	March	244 days	30
88	Albuquerque, NM	Tree (Jan–Apr)	January	274 days	30
89	Las Vegas, NV	Tree (Jan–Apr)	January	274 days	30
90	Tucson, AZ	Tree (Jan–Apr)	January	274 days	30
91	El Paso, TX	Tree (Jan–Apr)	January	274 days	30
92	Denver, CO	Tree (Mar–May)	March	244 days	27
93	Salt Lake City, UT	Tree (Mar–May)	March	244 days	27
94	Colorado Springs, CO	Tree (Mar–May)	March	244 days	27
95	Provo, UT	Tree (Mar–May)	March	244 days	27
96	Ogden, UT	Tree (Mar–May)	March	244 days	27
97	Spokane, WA	Tree (Apr–Jun)	April	213 days	27
98	Phoenix, AZ	Tree (Jan–Apr)	January	274 days	26
99	Mesa, AZ	Tree (Jan–Apr)	January	274 days	26
100	Boise, ID	Ragweed (Aug–Oct)	April	213 days	21

“Worst allergen” is the pollen type with the highest modeled load (peak intensity × season length) and its peak-month window. “Season starts” is the first month of the year with any active pollen; “season length” is the total active window across all three allergens. Load index = the sum of (peak × months in season) for tree, grass, and ragweed.

Frequently asked

What is the WeatherStory Allergy Index?: It is a modeled seasonal pollen-load ranking of the 100 largest U.S. metropolitan areas. For each metro it scores modeled tree, grass, and ragweed intensity against how long each season lasts, then sums the three into one load index. It is inspired by AAFA's long-running Allergy Capitals report but built from a transparent, always-current seasonal model rather than a proprietary yearly score.
Is this the same as AAFA's Allergy Capitals?: No. AAFA's Allergy Capitals report also weights over-the-counter allergy-medicine use and the number of board-certified allergists in each metro. The WeatherStory Allergy Index computes only modeled seasonal pollen load, from regional season windows and each city's latitude rather than measured daily counts. Read it as a related but different, transparently reproducible ranking — not a copy of AAFA's number.
Which U.S. metro ranks #1 in 2026?: Miami, Florida tops the 2026 index with a seasonal load index of 54. Its worst allergen is grass, whose season runs about 365 days, and its overall active-pollen window spans roughly 365 days a year.
When does allergy season start?: It depends where you live, which is why this report includes an onset map. In the warm South and West, tree and grass pollen can be active as early as January; across the northern tier, tree pollen usually leads in March or April. The map colors each state by the typical first month of the year with active pollen among its ranked metros. Enter your ZIP to see your nearest metro's onset month.
How long is the typical pollen season?: Across the 100 ranked metros, the median active-pollen window — any of tree, grass, or ragweed at Low or above — is about 274 days, and 13 metros run a near-year-round season of 330+ days. Warm, humid metros that stack tree, grass, and ragweed back to back carry the longest seasons; short, cold, or dry climates carry the shortest.
How accurate is the ranking?: It is a model, not a measurement. The intensity values come from published regional season windows (AAFA/ACAAI) shifted by latitude (Hopkins' bioclimatic law), not from a pollen-counting station in each city, so treat small rank gaps between neighbors as noise, not precision. The value is transparency: the formula is published on the methodology page, so anyone can trace why a metro lands where it does.
Can I republish the ranking?: Yes — with attribution. Please credit "WeatherStory Allergy Index 2026, edition 2026.2 (weatherstory.io/allergy-index/2026)" and link the methodology page. A recommended citation line is provided at the bottom of this report. Quote the edition number too: the ranking is recomputed when the model changes, and the 2026.1 run had a different #1.

Recommended citation

WeatherStory Allergy Index 2026, edition 2026.2. Weather Story, published 2026-07-11, revised 2026-09-16. A modeled seasonal pollen-load ranking of the 100 largest U.S. metropolitan areas. https://weatherstory.io/allergy-index/2026. Methodology: https://weatherstory.io/methodology.

Cite the edition number as well as the year: the ranking is recomputed whenever the model changes, and 2026.2 is not 2026.1 (see what changed in 2026.2).

More pollen & allergy data

See the always-current worst cities for allergies ranking, the pollen & allergy statistics hub, or browse pollen counts by city for the full per-city tree, grass, and ragweed calendars.