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Major US Cities Threatened by Excessive Heat

Major US Cities Threatened by Excessive Heat

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65. Provo, UT

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64. Los Angeles, CA

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63. El Cajon, CA

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62. Sunnyvale, CA

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61. Escondido, CA

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60. Boise City, ID

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59. West Jordan, UT

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58. Salt Lake City, UT

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57. El Monte, CA

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56. Meridian, ID

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55. Thousand Oaks, CA

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54. Santa Clara, CA

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53. West Covina, CA

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52. Burbank, CA

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51. Nampa, ID

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50. West Valley City, UT

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49. San Jose, CA

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48. Corona, CA

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47. Temecula, CA

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46. Pasadena, CA

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45. Pomona, CA

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44. Glendale, CA

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43. Murrieta, CA

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42. Reno, NV

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41. Ontario, CA

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40. Simi Valley, CA

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39. Jurupa Valley, CA

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38. Riverside, CA

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37. Menifee, CA

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36. Sparks, NV

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35. Rancho Cucamonga, CA

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34. Fontana, CA

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33. Rialto, CA

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32. Moreno Valley, CA

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31. Santa Clarita, CA

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30. Concord, CA

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29. San Bernardino, CA

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28. Palmdale, CA

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27. Antioch, CA

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26. Bakersfield, CA

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25. Victorville, CA

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24. Modesto, CA

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23. Tucson, AZ

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22. Lancaster, CA

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21. Vacaville, CA

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20. Stockton, CA

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19. Elk Grove, CA

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18. Sacramento, CA

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17. Scottsdale, AZ

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16. Roseville, CA

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15. Las Vegas, NV

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14. Chico, CA

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13. Fresno, CA

Source: Jacob Boomsma / Shutterstock.com

12. Peoria, AZ

Source: Matt Gush / Shutterstock.com

11. Visalia, CA

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10. Clovis, CA

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9. North Las Vegas, NV

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8. Mesa, AZ

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7. Gilbert, AZ

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6. Surprise, AZ

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5. Phoenix, AZ

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4. Chandler, AZ

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3. Tempe, AZ

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2. Henderson, NV

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1. Glendale, AZ

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65. Provo, UT
64. Los Angeles, CA
63. El Cajon, CA
62. Sunnyvale, CA
61. Escondido, CA
60. Boise City, ID
59. West Jordan, UT
58. Salt Lake City, UT
57. El Monte, CA
56. Meridian, ID
55. Thousand Oaks, CA
54. Santa Clara, CA
53. West Covina, CA
52. Burbank, CA
51. Nampa, ID
50. West Valley City, UT
49. San Jose, CA
48. Corona, CA
47. Temecula, CA
46. Pasadena, CA
45. Pomona, CA
44. Glendale, CA
43. Murrieta, CA
42. Reno, NV
41. Ontario, CA
40. Simi Valley, CA
39. Jurupa Valley, CA
38. Riverside, CA
37. Menifee, CA
36. Sparks, NV
35. Rancho Cucamonga, CA
34. Fontana, CA
33. Rialto, CA
32. Moreno Valley, CA
31. Santa Clarita, CA
30. Concord, CA
29. San Bernardino, CA
28. Palmdale, CA
27. Antioch, CA
26. Bakersfield, CA
25. Victorville, CA
24. Modesto, CA
23. Tucson, AZ
22. Lancaster, CA
21. Vacaville, CA
20. Stockton, CA
19. Elk Grove, CA
18. Sacramento, CA
17. Scottsdale, AZ
16. Roseville, CA
15. Las Vegas, NV
14. Chico, CA
13. Fresno, CA
12. Peoria, AZ
11. Visalia, CA
10. Clovis, CA
9. North Las Vegas, NV
8. Mesa, AZ
7. Gilbert, AZ
6. Surprise, AZ
5. Phoenix, AZ
4. Chandler, AZ
3. Tempe, AZ
2. Henderson, NV
1. Glendale, AZ

Much like the rest of the world, the United States is getting warmer. This increase in heat is due to climate change caused by several factors but the most significant modifier is greenhouse gases. Many of these gases may occur naturally, but several, like carbon dioxide (CO2), methane, nitrous oxide, and fluorinated gases, are a result of human activities. This temperature rise has led to excessive heat and dangerous weather conditions. According to one report, Summer 2024 was the warmest on record in the Northern Hemisphere.

When gauging how hot it is, it's important to factor in both the temperature and heat index. According to the National Weather Service, the heat index, a measure of heat and humidity, is what the temperature feels like to the human body when relative humidity is combined with the air temperature. In the sun, a person could perceive the temperature as being up to 15 degrees F warmer. For anyone who has lived on both the East and West Coasts, the difference between dry heat and humid heat is significant.

The National Weather Service categorizes a heat index of 80-90 degrees as "Caution," 90-103 degrees as "Extreme Caution," and 103-125 as "Danger." In the "danger" zone of 103-125 degree heat index, heat cramps or heat exhaustion is likely, with heat stroke possible after long exposure or exercise. Above 125 degrees, heat stroke is highly likely.

To determine major U.S. cities threatened by excessive heat, 24/7 Tempo reviewed data on current weather warnings and advisories from the NOAA's National Weather Service. Cities whose land area falls at least 50% within the boundaries of an NWS excessive heat warning as of July 11, 2024, were ordered by maximum observed temperature during the period July 1-8, 2024.

Temperature data is from the NOAA's nClimGrid-Daily program and was aggregated from the census tract level to the place level using boundary definitions from the U.S. Census Bureau's TIGER/Line shapefiles program. Only cities with at least 100,000 residents were considered. Population data is from the Census Bureau's 2022 American Community Survey.

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