The National Oceanic and Atmospheric Administration (NOAA) confirmed on Monday, August 8, 2024, that July 2024 was the hottest month ever recorded in the contiguous United States. The average temperature across the Lower 48 states reached 76.9°F (24.94°C), surpassing the previous record set in July 1936 by 0.1 to 0.2 degrees.
Every state in the contiguous U.S. recorded temperatures at least 1°F above the 20th-century average, according to NOAA’s National Centers for Environmental Information (NCEI). The data, dating back to 1895, marks the first time a monthly average has exceeded 76°F in the U.S.
Record-Breaking Heatwaves and Climate Context
The extreme temperatures were driven by three major heat dome events that trapped hot air over large regions, including the West, Rockies, Upper Midwest, Gulf Coast, and Southeast. Scientists attribute the severity of the heat to human-driven climate change, which has increased the frequency, intensity, and duration of extreme heat events.
Wyoming experienced its hottest July on record, with average temperatures 5.1°F above normal, while Salt Lake City, Utah, recorded an all-time high of 109°F on July 12. The average nighttime low temperature across the Lower 48 also set a record at 64.2°F, surpassing the previous high by 0.7°F. Experts warn that unusually warm nights prevent the human body from recovering from daytime heat, increasing health risks.
Widespread Impacts on Daily Life and Infrastructure
More than 185 million people were under heat alerts during the month, including residents of major cities such as Boston, New York, Philadelphia, and Washington, D.C. Several public events, including Washington, D.C.’s Independence Day parade, were canceled or postponed due to extreme heat.
The extreme temperatures also contributed to heavy rainfall and flooding in some regions, including Texas and New York, despite the third-driest July on record for precipitation across the contiguous U.S. As of August 4, 48.5% of the contiguous U.S. was in drought, with Puerto Rico reporting over two-thirds of the island under drought conditions. Water rationing has begun in San Juan and surrounding communities.
State-by-State Breakdown of Record Heat
A NOAA map released with the report shows above-average temperatures across all 48 contiguous states, with 13 states experiencing one of their five warmest Julys on record. Key regional highlights include:
- Alabama: Temperatures were generally above average, with some near-average areas in the north.
- Arizona: Much of the state experienced much above average temperatures, particularly in the south and north.
- California: Southern California saw much above average temperatures, while central and northern regions were in the above-average category.
- Wyoming and Montana: Both states recorded all-time high temperatures, with Wyoming setting a new monthly record.
Scientific Consensus on Climate Change
Climate scientists emphasize that the record-breaking heat aligns with long-term trends linked to global warming. Rising greenhouse gas emissions have intensified heat waves, making them more frequent, longer-lasting, and more severe. The Intergovernmental Panel on Climate Change (IPCC) has previously warned that such extreme weather events will become more common without significant reductions in emissions.
NOAA’s findings reinforce broader global data, including reports from the Copernicus Climate Change Service, which confirmed that July 2024 was the hottest month globally since records began. The agency noted that ocean temperatures and land heatwaves contributed to the unprecedented warmth.