Allergy season is getting longer and more severe in dozens of US cities: Here's where

(NEXSTAR) – If you're suffering from allergies right now, we've got some bad news for you. Chances are you live in a city where the allergy season is growing longer and worse.

That's because as the climate has warmed, there are fewer days with hard freezes. That gives pollen producers, grasses and weeds a longer period of time to thrive (and make your eyes water). The 2024 season has kicked off especially early, experts say.

It's not just that allergy season is growing longer – there's also evidence it's getting more intense. One study looked at the impact of increased carbon dioxide on ragweed plants. It found that with more carbon dioxide in the environment, ragweed plants grew larger and produced significantly more pollen.

Climate Central, an organization of scientists and journalists that studies the impacts of climate change, analyzed data from nearly 200 U.S. cities to determine where the allergy problems are growing worse. They found that since 1970, the allergy season has grown longer in 164 cities.

On average, these cities saw the season lengthen by 19 days.

The cities where allergy season lengthened the most since 1970 were:

1. Reno, Nevada: 95 days longer
2. Las Cruces, New Mexico: 65 days longer
3. Medford, Oregon: 61 days longer
4. Boise, Idaho: 51 days longer
5. Tupelo, Mississippi: 50 days longer
6. Missoula, Montana: 48 days longer
7. Myrtle Beach, South Carolina: 48 days longer
8. El Paso, Texas: 47 days longer
9. Toledo, Ohio: 45 days longer
10. Eugene, Oregon: 40 days longer
11. Helena, Montana: 40 days longer
12. Concord, New Hampshire: 39 days longer
13. Albuquerque/Santa Fe, New Mexico: 37 days longer
14. Roanoke, Virginia: 37 days longer
15. Manchester, New Hampshire: 35 days longer
16. Duluth, Minnesota: 34 days longer
17. Atlanta, Georgia: 33 days longer
18. Lansing, Michigan: 33 days longer
19. Minneapolis/St. Paul: 33 days longer
20. Madison, Wisconsin: 32 days longer

While 164 U.S. cities were found to have their allergy seasons growing longer, about 30 cities saw the opposite trend: shorter allergy seasons since 1970. Chief among them was Ottumwa, Iowa, where the allergy season is about 19 days shorter than it used to be.

There isn't one clear cause for why that may be the case, explained Climate Central meteorologist Lauren Casey. While global warming is happening globally, the impact at the local level isn't always clear-cut and predictable.

"I think of global warming as a big umbrella. We're seeing our global average temperatures increasing over time due to carbon pollution, but the effect of that is climate change. And that doesn't always necessarily just mean warming in a given location. It has all sorts of different and cascading effects," Casey said.

Waco, Texas; Tulsa, Oklahoma; Macon, Georgia; and Mobile, Alabama, also saw their allergy seasons cut down, according to the analysis.

It can also be harder to analyze the length of allergy seasons in the South and Southeast, Casey said, because some of the cities never drop below freezing, or only do so rarely.

Another recent report, released by the Asthma and Allergy Foundation of America, focused on where allergy sufferers have it worst overall. They found cities in the South and Midwest tend to have the worst allergy conditions. Wichita, Kansas, topped the list, followed by Virginia Beach, Virginia, and Greenville, South Carolina.