News

Grass Pollen Stays Elevated Across the West and Texas as Midwest Mold Builds

June 27, 2026 by PollenScience Staff

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.

National Overview

Grass remains the broadest outdoor allergy problem. The West carried the clearest burden, led by Seattle at Very High and high grass in Eugene, Missoula, and Portland. Texas also had a notable grass pocket, with Austin Georgetown and both Waco stations elevated, even though Oklahoma City slipped below high.

The Midwest was mixed for grass: Greenfield stayed high and Austin, Minnesota appeared in the high range, while Chicago dropped to moderate. Greenville remained the Southeast's main high grass station. In the Northeast, grass moved out of the higher range after Olean slipped to moderate.

Mold stayed important but more localized. Chicago remained high, St. Louis and Oklahoma City rose to high, and San Antonio East slipped from last week's peak while remaining elevated. Austin Georgetown's mold readings moved lower. Available Southeast, West, Northeast, and Puerto Rico mold readings were low.

Tree pollen looks increasingly late-season and uneven. The remaining high locations were Anchorage South, Missoula, Reno, and Greenfield. Puerto Rico's Caguas and San Juan moved down from high to moderate, and the Northeast no longer had high tree readings. Weed pollen has not broadly arrived; Seattle and Madison were the two high exceptions.

High Allergy Burden Locations

Location Allergen Level Drivers
Seattle, WA Grass Very High Grass Family, all types
Anchorage (South), AK Tree High Alder
Austin (Georgetown), TX Grass High Grass Family, all types
Austin, MN Grass High Grass Family, all types
Chicago (Melrose Park), IL Mold High Ascospores
Eugene, OR Grass High Grass Family, all types
Greenfield, WI Grass High Grass Family, all types
Greenfield, WI Tree High Pine Family with air bladders
Greenville, SC Grass High Other identified grass pollen
Madison, WI Weed High Cattail
Missoula, MT Grass High Grass Family, all types
Missoula, MT Tree High Pine Family with air bladders
Oklahoma City, OK Mold High Ascospores
Portland, OR Grass High Grass Family, all types
Reno (Sparks), NV Tree High Pine Family with air bladders
San Antonio (East), TX Mold High Other identified fungi
Seattle, WA Weed High Nettle family, Pellitory
St. Louis (Berkeley), MO Mold High Ascospores
Waco (Woodway North), TX Grass High Grass Family, all types
Waco (Woodway South), TX Grass High Grass Family, all types

Pollen Drivers

Mold pressure was led by ascospores in Chicago, St. Louis, and Oklahoma City. San Antonio East's high mold reading came from other identified fungi, a step down from its Very High peak but still meaningful for sufferers.

Tree pollen was narrower than earlier in the season. Pine-family pollen accounted for the high tree readings in Missoula, Reno, and Greenfield, while Anchorage South's high tree reading came from alder. Weed pollen was still limited, with Seattle driven by nettle-family and pellitory pollen and Madison driven by cattail.

Weather Context

South Central weather turned warmer and much drier, which coincided with grass moving higher at Austin Georgetown and Waco Woodway North. Mold was split in the same region: Oklahoma City rose to high, while San Antonio East and Austin Georgetown stepped down but did not disappear.

The West was cooler but wetter than last week. That coincided with grass staying active in Seattle, Eugene, Missoula, and Portland, while tree pollen became more uneven: Anchorage South and Reno moved higher, but Colorado Springs and Fairbanks moved lower.

The Midwest became wetter with lighter winds, coinciding with mold rising in St. Louis and staying high around Chicago. The Southeast stayed warm and wet but mostly quiet outside Greenville grass, while the Northeast and Puerto Rico moved out of the higher tree and grass ranges.

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