Counties with the most 100-degree days in March

By Sam Stebbins  •  April 6, 2026
a view of a mountain range from the bottom of a canyon
Photo by Valerie Sidorova on Unsplash

Each year, spring officially begins between March 19th and 21st. With most of March falling in the winter season, the month is typically among the coldest in the United States. According to the National Oceanic and Atmospheric Administration, the average March temperature across the Lower 48 was 41.5°F during the 20th century – well below the average annual temperature of 52°F. But in the era of climate change, dangerously high temperatures typically associated with summer are now arriving far sooner in some parts of the country. 

According to local weather station data compiled by NOAA, record-high March temperatures were either matched or broken in the U.S. 2,235 times in 2026. At many high-elevation weather stations, record-breaking March temperatures were in the mid- to high-50s. But in other parts of the Southern and Western United States, temperatures last month regularly surged past 100°F. 

In half a dozen states, including Arizona, California, Kansas, and Oklahoma, multiple counties reported 100-plus degree March temperatures in 2026. Heat is the leading cause of weather-related fatalities in the United States, and when the mercury rises into the triple digits, risks increase substantially. Between 2020 and 2024 alone, at least 1,840 fatalities nationwide were attributed to high temperatures, according to the National Weather Service. 

The heatwave of March 2026 is inextricably linked to human-caused climate change, and according to researchers at the Yale Center for Environmental Communication, such an event would not likely have been possible in the 20th century. Multiple U.S. counties reported a week or more of 100-plus degree days last month, far exceeding historically normal monthly highs in the 50s or 60s. 

Using data from NOAA, Climate Crisis 247 identified the U.S. counties reporting the most days of 100°F temperatures or higher in March 2026. We listed all 10 counties with nine or more days of triple digit temperatures, along with the reporting weather stations. County-level, average daily highs in the month of March during the 20th century are as reported by NOAA’s Climate at a Glance program. 

The 10 counties on this list span four states: Arizona, California, Nevada, and Texas. These places reported as many as 12 days with 100-plus degree temperatures last month, and maximum temperatures in March 2026 ranging from 104°F to 112°F – exceeding 20th century norms by as much as 50°F.

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Photo by EcoNaturalist.com on Unsplash

10. Brewster County, Texas

  • 100°F-plus temperature days in March 2026: 9
  • Reported by: Rio Grande Village Weather Station
  • Highest temperature in March 2026: 104°F on March 27
  • Reported by: Rio Grande Village Weather Station
  • Average daily high in Brewster County, March 1901-2000: 66.6°F

9. Maricopa County, Arizona

  • 100°F-plus temperature days in March 2026: 9
  • Reported by: Phoenix Airport and Tempe ASU Weather Stations
  • Highest temperature in March 2026: 107°F on March 20
  • Reported by: Buckeye 5N Weather Station
  • Average daily high in Maricopa County, March 1901-2000: 68.0°F

8. Pima County, Arizona

  • 100°F-plus temperature days in March 2026: 9
  • Reported by: AJO and Organ Pipe Cactus NM Weather Stations
  • Highest temperature in March 2026: 110°F on March 21
  • Reported by: AJO Weather Station
  • Average daily high in Pima County, March 1901-2000: 66.7°F

7. Mohave County, Arizona

  • 100°F-plus temperature days in March 2026: 10
  • Reported by: Havasu Arizona Weather Station
  • Highest temperature in March 2026: 107°F on March 20
  • Reported by: Havasu Arizona Weather Station
  • Average daily high in Mohave County, March 1901-2000: 57.4°F

6. Yuma County, Arizona

  • 100°F-plus temperature days in March 2026: 10
  • Reported by: Yuma Proving Ground and Tacna 3 NE Weather Stations
  • Highest temperature in March 2026: 109°F on March 20
  • Reported by: Yuma MCAS Weather Station
  • Average daily high in Yuma County, March 1901-2000: 71.0°F

5. Clark County, Nevada

  • 100°F-plus temperature days in March 2026: 11
  • Reported by: Laughlin Weather Station
  • Highest temperature in March 2026: 106°F on March 21
  • Reported by: Laughlin Weather Station
  • Average daily high in Clark County, March 1901-2000: 58.0°F

4. Inyo County, California

  • 100°F-plus temperature days in March 2026: 11
  • Reported by: Death Valley National Park Weather Station
  • Highest temperature in March 2026: 107°F on March 21
  • Reported by: Death Valley National Park Weather Station
  • Average daily high in Inyo County, March 1901-2000: 62.1°F

3. Riverside County, California

  • 100°F-plus temperature days in March 2026: 11
  • Reported by: Rice Valley California Weather Station
  • Highest temperature in March 2026: 108°F on March 20-21
  • Reported by: Desert Resorts Regional AP and Palm Springs ASOS Weather Stations
  • Average daily high in Riverside County, March 1901-2000: 69.9°F

2. Imperial County, California

  • 100°F-plus temperature days in March 2026: 11
  • Reported by: Buttercup California and Cahuilla California Weather Stations
  • Highest temperature in March 2026: 112°F on March 20
  • Reported by: Buttercup Weather Station
  • Average daily high in Imperial County, March 1901-2000: 77.0°F

1. San Bernardino County, California

  • 100°F-plus temperature days in March 2026: 12
  • Reported by: Iron Mountain Weather Station
  • Highest temperature in March 2026: 108°F on March 21
  • Reported by: Iron Mountain Weather Station
  • Average daily high in San Bernardino County, March 1901-2000: 67.1°F


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