The United States spans an enormous range of climates — from the subtropical heat of South Florida to the subarctic chill of interior Alaska, from the arid deserts of the Southwest to the rain-soaked Pacific Northwest. Understanding these climate patterns at the county level helps homebuyers, retirees, remote workers, and businesses make informed decisions about where to locate.
Using 30-year climate normals from NOAA (1991-2020), we analyzed weather data for 3,139 US counties. The national average annual temperature across all counties with data is 54.8°F, but that number masks extraordinary variation.
The Hottest Counties in America
The hottest counties are concentrated in the desert Southwest and South Florida. Monroe County, FL leads with an average annual temperature of 77.87272727272726°F. These counties experience extreme heat days numbering in the dozens or even hundreds per year.
| Rank | County | State | Avg Temp (°F) | July Avg (°F) | Heat Days |
|---|---|---|---|---|---|
| 1 | Monroe County | FL | 77.87272727272726 | 84.45454545454547 | 66.57272727272726 |
| 2 | Broward County | FL | 76.7 | 83.575 | 77.675 |
| 3 | Miami-Dade County | FL | 76.55384615384615 | 83.43076923076924 | 85.93846153846152 |
| 4 | Starr County | TX | 75.5 | 88.25 | 190.75 |
| 5 | Collier County | FL | 75.31428571428572 | 83.2 | 119.21428571428572 |
| 6 | Lee County | FL | 75.2 | 82.95 | 119.7 |
| 7 | Palm Beach County | FL | 75.05714285714285 | 82.75714285714287 | 86.27142857142857 |
| 8 | Charlotte County | FL | 75.05 | 83.8 | 129.95 |
| 9 | Cameron County | TX | 75.03333333333335 | 85.28333333333335 | 120.96666666666664 |
| 10 | Hidalgo County | TX | 74.84444444444443 | 86.45555555555556 | 171.27777777777774 |
The Coldest Counties in America
At the other extreme, the coldest counties are found in Alaska, northern Minnesota, and the northern Great Plains. North Slope Borough, AK has an average annual temperature of just 14.485714285714286°F. January averages in these counties can drop well below zero.
| Rank | County | State | Avg Temp (°F) | Jan Avg (°F) | Snowfall (in) |
|---|---|---|---|---|---|
| 1 | North Slope Borough | AK | 14.485714285714286 | -12.6 | 46.29999999999999 |
| 2 | Northwest Arctic Borough | AK | 23.35 | -1.5499999999999998 | 64.2 |
| 3 | Yukon-Koyukuk Census Area | AK | 25.281818181818185 | -9.227272727272728 | 77.9 |
| 4 | Southeast Fairbanks Census Area | AK | 26.127272727272725 | -8.254545454545456 | 41.488888888888894 |
| 5 | Copper River Census Area | AK | 27.842857142857145 | -2.7857142857142856 | 62.23333333333333 |
| 6 | Denali Borough | AK | 28 | -0.7 | 76.7 |
| 7 | Nome Census Area | AK | 28 | 5.6 | 80.8 |
| 8 | Fairbanks North Star Borough | AK | 28.53684210526316 | -4.58421052631579 | 60.15 |
| 9 | Bethel Census Area | AK | 31.4 | 6.9 | 64 |
| 10 | Kusilvak Census Area | AK | 31.4 | 6.9 | 64 |
Precipitation Patterns: Where It Rains the Most
Precipitation varies dramatically across the country. The wettest counties receive over 60 inches of rain annually, concentrated in the Gulf Coast, the Pacific Northwest, and the Appalachian Mountains. The driest counties in the desert Southwest may receive fewer than 5 inches per year.
| Rank | County | State | Annual Precip (in) | Snowfall (in) | Avg Temp (°F) |
|---|---|---|---|---|---|
| 1 | Ketchikan Gateway Borough | AK | 153.405 | N/A | 46.65 |
| 2 | Sitka City and Borough | AK | 152.75666666666666 | 101.8 | 43.93333333333334 |
| 3 | Yakutat City and Borough | AK | 140.36 | 147.3 | 41.1 |
| 4 | Chugach Census Area | AK | 139.07875 | 221.18 | 40.3125 |
| 5 | Petersburg Borough | AK | 110.19 | 85.6 | 43 |
| 6 | Prince of Wales-Hyder Census Area | AK | 104.91166666666668 | 45.4 | 45 |
| 7 | Grays Harbor County | WA | 100.27142857142856 | 0.5 | 50.557142857142864 |
| 8 | Skamania County | WA | 95.82333333333332 | 25.8 | 50.56666666666666 |
| 9 | Pacific County | WA | 94.48 | 1.225 | 50.47500000000001 |
| 10 | Hoonah-Angoon Census Area | AK | 93.856 | 96 | 41.92 |
Regional Climate Zones
The county-level data reveals distinct climate zones that correlate closely with geography:
- Pacific Coast: Mild year-round temperatures with moderate rainfall. Counties along the California coast have some of the smallest seasonal temperature swings in the country.
- Desert Southwest: Extreme heat, minimal precipitation, large day-night temperature swings. Arizona and Nevada counties regularly exceed 100°F in summer.
- Gulf Coast: Hot, humid summers with heavy rainfall and mild winters. Counties from Texas to Florida receive 50-65 inches of rain annually.
- Great Plains: Extreme seasonal variation — cold winters and hot summers. Counties in Kansas, Nebraska, and the Dakotas can see 100°F+ temperature swings between January and July.
- Northeast and Midwest: Four distinct seasons with moderate-to-heavy snowfall. Counties across New England and the Great Lakes region see 40-100+ inches of snow per year.
- Mountain West: Elevation-dependent climate — cool summers, cold winters, low humidity. Colorado and Montana counties at elevation enjoy dry, comfortable summers.
Methodology
All data comes from NOAA National Centers for Environmental Information (NCEI), using the 1991-2020 U.S. Climate Normals. Climate normals are 30-year averages representing typical conditions. Station-level data is aggregated to county level using spatial averaging. Approximately 89% of US counties have sufficient weather station coverage for reliable data.
Data source: NOAA National Centers for Environmental Information (NCEI), U.S. Climate Normals 1991-2020. All figures represent 30-year averages and may differ from individual-year observations. Station-level data is aggregated to county level using spatial averaging.