US cities where Climate Change Is making Allergy seasons much longer

By Evan Comen  •  May 6, 2026
a person holding a pack of pills in their hand
Photo by Simon Kadula on Unsplash

A warming climate means longer allergy seasons. As temperatures below freezing become a rarer occurrence and global ice cover contracts, trees, grasses, and weeds have more time to grow and more time to release allergy-triggering pollen. Together with rising carbon dioxide levels, which can stimulate plants to produce more pollen, rising temperatures are creating worsening health burdens for allergy-prone individuals.

The intensity of pollen in a given year is positively correlated with length of the growing season – also measured as the number of days with temperatures above freezing. The number of freeze-free days is rising around the world, with the growing seasons in some regions forecast to last over a month longer this year compared to 50 years ago. A closer look at a recent analysis by Climate Central reveals the cities where rising temperatures are contributing to worsening allergy seasons throughout the United States.

To determine the cities where rising temperatures are contributing to longer allergy seasons, Climate Crisis 247 reviewed data from a recent analysis by Climate Central. Cities were ranked based on the change in the average annual number of consecutive days with minimum temperatures above 32°F from the decade 1970-1979 to the decade 2015-2025. Data are based on historical station-level readings from the Applied Climate Information System, a program of the NOAA.

16. Tyler, TX

  • Avg. growing season length, 2015-24: 260 days (+15.0% from 1970-79)
  • Avg. growing season length, 1970-79: 226 days
  • Climate region: South

15. Prescott, AZ

  • Avg. growing season length, 2015-24: 189 days (+14.5% from 1970-79)
  • Avg. growing season length, 1970-79: 165 days
  • Climate region: Southwest
Aerial view of Sacramento's downtown skyline at sunset with vibrant autumn foliage.
Photo by Stephen Leonardi on Pexels

14. Albuquerque-Santa Fe, NM

  • Avg. growing season length, 2015-24: 214 days (+16.3% from 1970-79)
  • Avg. growing season length, 1970-79: 184 days
  • Climate region: Southwest

13. Raleigh-Durham, NC

  • Avg. growing season length, 2015-24: 225 days (+19.0% from 1970-79)
  • Avg. growing season length, 1970-79: 189 days
  • Climate region: Southeast

12. Eugene, OR

  • Avg. growing season length, 2015-24: 215 days (+27.2% from 1970-79)
  • Avg. growing season length, 1970-79: 169 days
  • Climate region: Northwest

11. Juneau, AK

  • Avg. growing season length, 2015-24: 154 days (+16.7% from 1970-79)
  • Avg. growing season length, 1970-79: 132 days
  • Climate region: Northwest

10. Bozeman, MT

  • Avg. growing season length, 2015-24: 117 days (+25.8% from 1970-79)
  • Avg. growing season length, 1970-79: 93 days
  • Climate region: Northern Rockies & Plains

9. Helena, MT

  • Avg. growing season length, 2015-24: 152 days (+28.8% from 1970-79)
  • Avg. growing season length, 1970-79: 118 days
  • Climate region: Northern Rockies & Plains

8. Marquette, MI

  • Avg. growing season length, 2015-24: 132 days (+24.5% from 1970-79)
  • Avg. growing season length, 1970-79: 106 days
  • Climate region: Upper Midwest

7. Toledo, OH

  • Avg. growing season length, 2015-24: 186 days (+26.5% from 1970-79)
  • Avg. growing season length, 1970-79: 147 days
  • Climate region: Ohio Valley

6. Tupelo, MS

  • Avg. growing season length, 2015-24: 237 days (+24.7% from 1970-79)
  • Avg. growing season length, 1970-79: 190 days
  • Climate region: South

5. Las Cruces, NM

  • Avg. growing season length, 2015-24: 253 days (+29.1% from 1970-79)
  • Avg. growing season length, 1970-79: 196 days
  • Climate region: Southwest
top view of an island
Photo by Derek Thomson on Unsplash

4. Concord, NH

  • Avg. growing season length, 2015-24: 154 days (+36.3% from 1970-79)
  • Avg. growing season length, 1970-79: 113 days
  • Climate region: Northeast

3. Medford, OR

  • Avg. growing season length, 2015-24: 213 days (+36.5% from 1970-79)
  • Avg. growing season length, 1970-79: 156 days
  • Climate region: Northwest

2. Missoula, MT

  • Avg. growing season length, 2015-24: 145 days (+39.4% from 1970-79)
  • Avg. growing season length, 1970-79: 104 days
  • Climate region: Northern Rockies & Plains

1. Reno, NV

  • Avg. growing season length, 2015-24: 190 days (+69.6% from 1970-79)
  • Avg. growing season length, 1970-79: 112 days
  • Climate region: West


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