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Grass Pollen Builds Across the South as Tree Pollen Stays Elevated From the Midwest to Puerto Rico
Spring tree pollen is now a national story: elevated readings stretched from Wisconsin and Nebraska to New Jersey, Kentucky, South Carolina, Alaska, Washington, and Puerto Rico. Grass became a big new irritant, with more high readings in the South Central, Southeast, Northeast, and parts of the West, while weeds and mold were mostly limited exceptions
National Overview
Tree pollen remained the broadest burden for allergy sufferers, especially in the Midwest and Puerto Rico. Five of seven Midwest stations reached elevated tree levels, led by Austin (MN), Chicago, Greenfield (WI), Madison (WI), and Omaha (NE). Puerto Rico stayed intense as well, with Caguas (PR) still in the top severity band and San Juan remaining elevated for trees while also adding high grass pollen.
Grass pollen became more noticeable across the southern half of the country. South Central readings were the most widespread, with Houston, Oklahoma City, Tulsa, and Waco (Woodway North, TX) all elevated. In the Southeast, Cincinnati, Greenville (SC), and Washington (Silver Spring, MD) also reached high grass levels. Union (NJ), Reno, Chicago, and St. Louis show that grass is no longer confined to one part of the map, but it is still more of a regional and metro-level problem than a fully national one.
Tree pollen is still active outside those main areas, but the pattern is uneven. The Southeast had elevated tree readings in Cincinnati, Greenville, and Washington, while the Northeast was mostly quieter except for Union. In the West, Fairbanks and Seattle reached high tree levels, pointing to a later-season northern and Pacific Northwest pickup rather than a broad Western peak.
Weeds were mostly quiet, with Tulsa the main high-level exception. Mold also stayed low or moderate in most places; San Antonio (East) was the only station to reach a high mold level.
High Allergy Burden Locations
| Location | Allergen | Level | Drivers |
|---|---|---|---|
| Caguas (Centro), PR | Tree | Very High | All identified tree pollen not counted elsewhere |
| Austin, MN | Tree | High | Maple, Box elder; Oak; Juniper family, Cedar |
| Chicago (Melrose Park), IL | Grass | High | Grass Family, all types |
| Chicago (Melrose Park), IL | Tree | High | Beech; Mulberry; Maple, Box elder |
| Cincinnati (Florence), KY | Grass | High | Grass Family, all types |
| Cincinnati (Florence), KY | Tree | High | Pine Family with air bladders |
| Fairbanks, AK | Tree | High | Poplar, Cottonwood, Aspen |
| Greenfield, WI | Tree | High | Oak; Maple, Box elder; Birch |
| Greenville, SC | Grass | High | All identified grass pollen not counted elsewhere |
| Greenville, SC | Tree | High | Pine Family with air bladders |
| Houston (Medical Center), TX | Grass | High | All identified grass pollen not counted elsewhere |
| Madison, WI | Tree | High | Oak |
| Oklahoma City, OK | Grass | High | Grass Family, all types |
| Oklahoma City, OK | Tree | High | Hickory, Pecan |
| Omaha (Bellevue), NE | Tree | High | Mulberry |
| Reno (Sparks), NV | Grass | High | All identified grass pollen not counted elsewhere |
| San Antonio (East), TX | Mold | High | Any identified fungi not counted elsewhere |
| San Juan, PR | Grass | High | Grass Family, all types |
| San Juan, PR | Tree | High | All identified tree pollen not counted elsewhere |
| Seattle, WA | Tree | High | Pine Family with air bladders; Juniper family, Cedar |
| St. Louis (Berkeley), MO | Grass | High | Grass Family, all types |
| Tulsa (South), OK | Grass | High | Grass Family, all types |
| Tulsa (South), OK | Weed | High | All identified weed pollen not counted elsewhere |
| Union, NJ | Grass | High | Grass Family, all types |
| Union, NJ | Tree | High | Maple, Box elder; Mulberry; Pine Family with air bladders |
| Waco (Woodway North), TX | Grass | High | Grass Family, all types |
| Washington (Silver Spring), MD | Grass | High | Grass Family, all types |
| Washington (Silver Spring), MD | Tree | High | Pine Family with air bladders |
Pollen Drivers
Tree pollen was mixed by region rather than dominated by one allergen nationally. In the Midwest, oak, maple/box elder, mulberry, birch, beech, and juniper or cedar all appeared among elevated readings. Oak remained important in Wisconsin and Madison, while mulberry helped carry the Omaha reading.
Pine-family pollen was the clearest named tree driver in the Southeast, showing up in Cincinnati, Greenville, and Washington. Union had a broader mix of maple/box elder, mulberry, and pine-family pollen. In South Central, the remaining elevated tree readings were narrower, with hickory/pecan driving Oklahoma City.
In the West, the later-season tree activity was more northern: poplar/cottonwood/aspen drove Fairbanks, while Seattle's elevated tree reading came from pine-family pollen and juniper or cedar.
Grass readings are typically reported in a broad category, so the main story is the spread of grass itself rather than a particular species.
Weather Context
Warmth and lighter rain coincided with the South Central grass buildup. The region stayed warm while rainfall was lower than the prior period, matching the rise in Houston and Waco and the continued high grass readings in Oklahoma City and Tulsa.
The Southeast stayed wet overall, but rain did not prevent high grass and tree readings in Cincinnati, Greenville, and Washington. In the Midwest, conditions turned warmer and much less wet than before, which lined up with continued elevated tree pollen and persistent high grass in Chicago and St. Louis.
Puerto Rico was warmer and much drier than before, and tree pollen remained intense. The West also warmed, while Alaska and Seattle stood out for tree pollen even as much of the region stayed below high levels.
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