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Grass Pollen Stays Active From the Midwest to the West as the Southeast and Reno Build

June 7, 2026 by PollenScience Staff

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.

National Overview

Grass pollen is still the most widespread burden for allergy sufferers. The Midwest and West carried the broadest pressure, with high grass readings clustered around Chicago, several Wisconsin cities, Eugene, Portland, Seattle, and Reno. Eugene remained the only grass location at Very High, while Reno moved into the high range and Pacific Northwest grass stayed elevated.

Grass also stayed active outside those two regions. Oklahoma City and Waco remained high in the South Central region, Washington and Richmond carried the Southeast and Mid-Atlantic burden, Olean stayed elevated in western New York, and San Juan remained active in Puerto Rico.

Tree pollen has largely shifted out of the broad Southern and Eastern peak pattern. The remaining elevated tree readings were concentrated in Alaska, Reno, Colorado Springs, Puerto Rico, and two Wisconsin stations. In the Northeast, Armonk and Olean slipped below high levels, suggesting the tree season is losing intensity there even as grass becomes more noticeable.

Mold remained a South Central concern but was less severe than last week. Austin and San Antonio stayed high, while San Antonio slipped from last week's peak and Oklahoma City moved below the high range. St. Louis was the main new mold pocket in the Midwest. Weeds stayed mostly quiet, with no reporting station reaching high weed levels.

High Allergy Burden Locations

Location Allergen Level Drivers
Eugene, OR Grass Very High Grass Family, all types
Anchorage (Midtown), AK Tree High Alder; Birch
Anchorage (South), AK Tree High Alder
Austin (Georgetown), TX Mold High Other identified fungi
Caguas (Centro), PR Tree High Other identified tree pollen
Chicago (Melrose Park), IL Grass High Grass Family, all types
Colorado Springs (North), CO Tree High Pine Family with air bladders
Fairbanks, AK Tree High Alder; Other identified tree pollen; Birch
Greenfield, WI Grass High Grass Family, all types
Greenfield, WI Tree High Birch; Pine Family with air bladders; Walnut, Butternut
La Crosse (Onalaska), WI Grass High Grass Family, all types
Madison, WI Grass High Grass Family, all types
Madison, WI Tree High Birch
Olean, NY Grass High Other identified grass pollen
Oklahoma City, OK Grass High Grass Family, all types
Portland, OR Grass High Grass Family, all types
Reno (Sparks), NV Grass High Grass Family, all types
Reno (Sparks), NV Tree High Pine Family with air bladders
Richmond, VA Grass High Grass Family, all types
San Antonio (East), TX Mold High Other identified fungi
San Juan, PR Grass High Grass Family, all types
San Juan, PR Tree High Other identified tree pollen
Seattle, WA Grass High Grass Family, all types
St. Louis (Berkeley), MO Mold High Ascospores
Waco (Woodway South), TX Grass High Grass Family, all types
Washington (Silver Spring), MD Grass High Grass Family, all types

Pollen Drivers

For trees, alder and birch carried much of the Alaska burden, while pine-family pollen remained important in Reno and appeared in Colorado Springs. Wisconsin's elevated tree readings included birch, pine-family pollen, and walnut/butternut.

Mold was led by other identified fungi in Austin and San Antonio. St. Louis was different, with ascospores accounting for the high mold reading. Weed pollen did not reach high levels at any reporting station, as weed pollen season remains early across much of the U.S.

Weather Context

Warm weather continued across the Midwest and South Central region, coinciding with persistent grass pressure in Chicago, Oklahoma City, and Waco. The South Central region also stayed wet, which coincided with mold remaining elevated in Austin and San Antonio even though San Antonio slipped from last week's peak.

The West turned warmer and drier, matching the continued grass activity in Eugene, Portland, Seattle, and Reno, along with elevated tree readings in Alaska, Colorado Springs, and Reno. The Northeast also turned warmer and much drier after a wetter stretch, but tree pollen there stayed below high levels while grass remained a more isolated concern.

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