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Weed pollen is the clearest late-summer burden for allergy sufferers. Wisconsin carried the broadest high-pressure cluster, with Greenfield, La Crosse, and Madison all reaching the high range. In the West, Reno also moved into high weed levels, while Colorado Springs and Riverton stayed active at moderate levels. Moderate weed pockets also appeared in the Midwest, South Central region, and parts of the Southeast, showing that the season is building unevenly rather than arriving everywhere at once.

Grass pollen remains the main outdoor burden for the broadest set of allergy sufferers. The strongest clusters were in the West, Midwest, and South Central region: Oregon, Washington, Montana, Wisconsin, Minnesota, Oklahoma, and parts of Texas all had high grass readings. Seattle slipped from last week's peak but stayed elevated, while La Crosse and Oklahoma City moved up into the high range and Austin, Greenfield, Eugene, Missoula, Portland, and Waco South held there.

Seattle was the lone Very High location, while Portland, Austin, and northern Waco joined the higher grass range. Mold pressure also mattered in Chicago, St. Louis, Oklahoma City, and San Antonio East; tree pollen and weeds were more scattered.

Palms are not a single uniform pollen problem across North America, but they can still matter to allergy sufferers in the places where they are common. In the United States, the strongest outdoor palm exposure is concentrated in Florida, the Gulf and south Atlantic coastal plain, the lower Rio Grande region, desert oasis habitats in the Southwest, Puerto Rico, Hawaii, and some frost-free subtropical landscapes where outdoor palms are long established.^1-7

Grass pollen remains the most widespread outdoor allergy burden. The West had the sharpest pressure, with Eugene and Seattle still Very High; Colorado Springs stayed high and Reno climbed into the high range. Midwest grass stayed elevated in Chicago and Greenfield, though La Crosse and Madison slipped below high levels, and South Central grass remained steady around Oklahoma City and Waco.

Eugene remained in the top severity band, while high grass readings held around Chicago, Wisconsin, Oklahoma City, Waco, San Juan, Portland, and Colorado Springs. Tree pollen is now mostly limited to the West and Puerto Rico, and mold was mainly a local issue in Austin, Chicago, and St. Louis.

Eugene remained the only station in the top severity band, and the high list also included Oklahoma, Texas, Puerto Rico, Olean, Washington, and Richmond. Tree pollen is now mostly a northern and western pocket issue, while mold stayed elevated in Austin and San Antonio and rose in St. Louis.

Eugene remained the sharpest grass location, while Wisconsin, Chicago, Portland, Seattle, Puerto Rico, and parts of Oklahoma and Texas stayed active. Tree pollen is now more concentrated in northern locations, while weeds are still mostly quiet.

Birches in the genus Betula are among the most recognizable spring-pollen trees in North America. For allergy sufferers, they matter because birch pollen is lightweight, readily airborne, and strongly associated with classic spring hay fever. In the United States, the biggest wild-birch exposure zones are the Northeast, Great Lakes, Upper Midwest, Alaska, and mountain West, but the birch story does not stop there. River birch extends the genus well into the Mid-Atlantic, Southeast, lower Midwest, and parts of south-central states, so birch-related exposure can appear outside the colder northern forest belt many patients expect.^1-3

Cincinnati also remained very high for grass pollen, while South Central readings held high around Oklahoma City, Tulsa, and Waco and Puerto Rico remained active for both grass and trees. Tree pollen has become more localized than earlier in spring; weeds were mostly quiet, but mold rose in Chicago, St. Louis, and San Antonio.

Grass pollen season started in earnest last week across a broad swath of the U.S., especially in the South and West, while the Midwest and Northeast still suffer from high tree pollen levels.

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

Tree pollen is still the biggest allergy problem for many readers, especially in the Midwest, Puerto Rico, and parts of the South Central region. The Midwest remains the broadest mainland trouble spot: five of seven current stations reached High or Very High tree pollen, with La Crosse still in the top band and Chicago, Greenfield, Madison, and Omaha also elevated.

Tree pollen is still the main burden for allergy sufferers, with the Midwest and Southeast carrying the most widespread elevated conditions. All eight current Midwest stations reached High or Very High tree pollen, and six of eight Southeast stations reached High. South Central tree pollen is less uniform but still active, with four of seven current stations elevated.

Hornbeam (Carpinus) and hop-hornbeam (Ostrya) are not the loudest tree-pollen story in North America, but they still matter to allergy sufferers because they belong to the same birch-family branch of the spring Fagales pollen season that includes alder, birch, and hazel.^1-7 In the United States, their combined outdoor range stretches across much of the eastern deciduous forest and then reappears in smaller canyon and mountain pockets of the Southwest.^1-4

Tree pollen is still the main problem for allergy sufferers this week. The worst current tree pressure is in the Southeast, where six of seven reporting stations reached High, and in the Northeast, where all four current stations did the same. The Midwest also remains firmly in tree season, with all six current stations at that level as well.

Tree pollen remained the main burden for allergy sufferers. The heaviest pressure was in Texas and Oklahoma, where seven of eight reporting South Central stations were still High or Very High, with the sharpest strain around Oklahoma City and San Antonio. The Southeast looked nearly as difficult, with seven of eight stations also elevated, led by Tampa and the Washington, D.C., suburbs. The Midwest stayed firmly in season as well, even though a few Wisconsin sites trended lower from last week.

Alders in the genus Alnus are common wetland, riparian, and cool-climate trees or shrubs across large parts of North America. For allergy sufferers, they matter because alder is one of the earlier tree-pollen sources of the year, especially in the Pacific Northwest, coastal Alaska, the Great Lakes, the Northeast, and streamside habitats in the East and Southeast.^1,2

Maple trees in the genus Acer are among the most widespread deciduous trees in temperate North America. Across the United States, Canada, and Puerto Rico, maples are common in forests, parks, and residential landscapes, making their pollen a regular component of the early-spring airborne allergen environment. The genus contains roughly 110–120 species globally, with about 12–15 native species in North America and several additional ornamental species planted widely in urban landscapes.¹