(NEXSTAR) – That extra head congestion you’ve been feeling lately may not all be in your head, so to speak.

A new report on seasonal allergies found the growing season has lengthened by more than two weeks, on average. A longer growing season means more days of sniffles, sneezes and headaches for allergy sufferers.

Climate Central, an organization of scientists and journalists focused on studying the impacts of climate change and warming global temperatures, analyzed temperature data from 203 U.S. cities since 1970.

They found allergy season isn’t just getting longer, it’s also getting more intense.

It’s largely because warming temperatures have essentially shortened the length of deep-freeze winters and extended the length of seasons where allergen-producing plants thrive.

“Earlier spring and longer periods of freeze-free days mean that plants have more time to flower and release allergy-inducing pollen,” Climate Central wrote in its report.

Of the 203 cities analyzed, 172 (about 85%) saw freeze-free seasons grow longer – many by more than a month.

The cities where allergy season has grown the most since 1970, according to the report, are:

  1. Reno, Nevada: 99 days longer
  2. Bend, Oregon: 83 days longer
  3. Las Cruces, New Mexico: 72 days longer
  4. Medford, Oregon: 63 days longer
  5. Boise, Idaho: 52 days longer
  6. Tupelo, Mississippi: 51 days longer
  7. El Paso, Texas: 50 days longer
  8. Myrtle Beach, South Carolina: 46 days longer
  9. Toledo, Ohio: 45 days longer
  10. Wheeling, West Virginia: 44 days longer
  11. Missoula, Montana: 42 days longer
  12. Albuquerque, New Mexico: 39 days longer
  13. Concord, New Hampshire: 39 days longer
  14. Eugene, Oregon: 38 days longer
  15. Jefferson City, Missouri: 38 days longer

The Centers for Disease Control and Prevention agrees climate change could lead people to suffer more health consequences from allergens. Pollen exposure could lead to symptoms of hay fever and allergic conjunctivitis, and could lead to more asthma attacks for people with asthma.

There were some cities among the 203 analyzed where the growing season is shortening, Climate Central’s scientists found. Ottumwa, Iowa; Denver, Colorado; and Waco, Texas all saw their growing seasons shorten by 15 or more days.