Most ER Visits Due To Heat Related Illness in the US From 2018 to 2025

The United States is now more than two weeks into the meteorological fall season, and recently released data from the preceding three months shows that the summer of 2026 was the hottest in U.S. history. According to the National Oceanic and Atmospheric Administration, the average temperature across the Lower 48 was 74.4°F from the beginning of June through the end of August—higher than in any year since at least 1895, and 3°F warmer than the 20th century average. 

The warming trend is particularly alarming as high summer temperatures are already the leading climate-related public threat in the United States. A recent study conducted by NPR and Boston University found that the average number of heat-related deaths in the U.S. may be as high 9,000 per year—a staggering figure that more than quadruples the official numbers published by the Centers for Disease Control and Prevention. 

As summer temperatures continue to rise, heat will likely take a growing toll on public health. A recent study conducted by the non-profit research and advocacy group Climate Central found that between the months of April in October, from 2018 to 2025, there were an average of 130 heat-related emergency room visits per day for every 100,000 ER visits nationwide. The report also found that 27% of heat-related ER visits in the last eight years were attributable to climate change. Perhaps not surprisingly, on some of the hottest summer days between 2018 and 2025, the estimated rate of heat-related ER visits surged. 

Using data from Climate Central, Climate Crisis 247 identified the days between 2018 and 2025 with the most heat-related ER visits. We ranked all calendar days included in the study on the total number of heat-related ER visits for every 100,000 ER visits. Calculations were made by summing regional rates by calendar day. Because calculations were not made using rates and not absolute totals, the numbers reflected in this story are approximate estimates only. All supplemental data in this story is from Climate Central.

10. June 27, 2021

• Approx. number of heat-related emergency room visits nationwide: 6,188 per 100,000 ER visits
• Estimated number of heat-related ER visits due to climate change nationwide: 1,669 per 100,000 ER visits
• U.S. region with the most heat-related ER visits: Northwest (Alaska, Idaho, Oregon, Washington)
• Number of heat-related ER visits in the Northwest: 4,180 per 100,000 ER visits (approx. 26.7% due to climate change)
• Average temperature in the Northwest: 95.5°F (2.0°F added by climate change)

9. June 22, 2024

• Approx. number of heat-related emergency room visits nationwide: 6,191 per 100,000 ER visits
• Estimated number of heat-related ER visits due to climate change nationwide: 1,658 per 100,000 ER visits 
• U.S. region with the most heat-related ER visits: Central Midwest (Iowa, Kansas, Missouri, Nebraska)
• Number of heat-related ER visits in the Central Midwest: 1,208 per 100,000 ER visits (approx. 20.5% due to climate change)
• Average temperature in the Central Midwest: 90.7°F (1.3°F added by climate change)

8. July 29, 2025

• Approx. number of heat-related emergency room visits nationwide: 6,205 per 100,000 ER visits
• Estimated number of heat-related ER visits due to climate change nationwide: 1,879 per 100,000 ER visits
• U.S. region with the most heat-related ER visits: Central Midwest (Iowa, Kansas, Missouri, Nebraska)
• Number of heat-related ER visits in the Central Midwest: 1,479 per 100,000 ER visits (approx. 19.7% due to climate change)
• Average temperature in the Central Midwest: 93.6°F (1.4°F added by climate change)

7. July 28, 2023

• Approx. number of heat-related emergency room visits nationwide: 6,327 per 100,000 ER visits
• Estimated number of heat-related ER visits due to climate change nationwide: 1,822 per 100,000 ER visits
• U.S. region with the most heat-related ER visits: Central Midwest (Iowa, Kansas, Missouri, Nebraska)
• Number of heat-related ER visits in the Central Midwest: 1,499 per 100,000 ER visits (approx. 21.6% due to climate change)
• Average temperature in the Central Midwest: 97.9°F (1.6°F added by climate change)

6. June 23, 2025

• Approx. number of heat-related emergency room visits nationwide: 7,088 per 100,000 ER visits
• Estimated number of heat-related ER visits due to climate change nationwide: 1,984 per 100,000 ER visits
• U.S. region with the most heat-related ER visits: Mid-Atlantic (Delaware, District of Columbia, Maryland, Pennsylvania, Virginia, West Virginia)
• Number of heat-related ER visits in the Mid-Atlantic: 1,412 per 100,000 ER visits (approx. 29.7% due to climate change)
• Average temperature in the Mid-Atlantic: 95.0°F (1.8°F added by climate change)

5. June 29, 2021

• Approx. number of heat-related emergency room visits nationwide: 7,109 per 100,000 ER visits
• Estimated number of heat-related ER visits due to climate change nationwide: 1,984 per 100,000 ER visits
• U.S. region with the most heat-related ER visits: Northwest (Alaska, Idaho, Oregon, Washington)
• Number of heat-related ER visits in the Northwest: 3,188 per 100,000 ER visits (approx. 27.6% due to climate change)
• Average temperature in the Northwest: 98.6°F (2.0°F added by climate change)

4. June 25, 2025

• Approx. number of heat-related emergency room visits nationwide: 8,110 per 100,000 ER visits
• Estimated number of heat-related ER visits due to climate change nationwide: 2,359 per 100,000 ER visits
• U.S. region with the most heat-related ER visits: Mid-Atlantic (Delaware, District of Columbia, Maryland, Pennsylvania, Virginia, West Virginia)
• Number of heat-related ER visits in the Mid-Atlantic: 1,710 per 100,000 ER visits (approx. 30.6% due to climate change)
• Average temperature in the Mid-Atlantic: 94.1°F (2.0°F added by climate change)

3. July 20, 2019

• Approx. number of heat-related emergency room visits nationwide: 8,119 per 100,000 ER visits
• Estimated number of heat-related ER visits due to climate change nationwide: 2,484 per 100,000 ER visits
• U.S. region with the most heat-related ER visits: Mid-Atlantic (Delaware, District of Columbia, Maryland, Pennsylvania, Virginia, West Virginia)
• Number of heat-related ER visits in the Mid-Atlantic: 1,645 per 100,000 ER visits (approx. 35.3% due to climate change)
• Average temperature in the Mid-Atlantic: 94.6°F (2.2°F added by climate change)

2. June 24, 2025

• Approx. number of heat-related emergency room visits nationwide: 8,764 per 100,000 ER visits
• Estimated number of heat-related ER visits due to climate change nationwide: 2,472 per 100,000 ER visits
• U.S. region with the most heat-related ER visits: New England per 100,000 ER visits (approx. Connecticut, Maine, Massachusetts, New Hampshire, Rhode Island, Vermont)
• Number of heat-related ER visits in the New England: 2,011 (26.4% due to climate change)
• Average temperature in the New England: 95.5°F (1.6°F added by climate change)

1. June 28, 2021

• Approx. number of heat-related emergency room visits nationwide: 9,328 per 100,000 ER visits
• Estimated number of heat-related ER visits due to climate change nationwide: 2,553 per 100,000 ER visits
• U.S. region with the most heat-related ER visits: Northwest (Alaska, Idaho, Oregon, Washington)
• Number of heat-related ER visits in the Northwest: 6,763 per 100,000 ER visits (approx. 27.1% due to climate change)
• Average temperature in the Northwest: 98.8°F (2.0°F added by climate change)