2024 Fall Package

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KEY CONCEPTS

• September 1 is the start of meteorological fall. The season has warmed across the U.S. 

• Fall has warmed in 234 U.S. cities — by 2.5°F on average since 1970.

• Unusually warm fall days now happen more often in 233 cities. And 97 cities now experience at least two more weeks worth of above-normal fall days than in 1970.

• Fall warming is widespread across the contiguous U.S., and most intense in the Southwest. 

• A warmer fall season prolongs risks of heat-related illness, wildfire, allergies, and more.

Record-warm oceans, active hurricane season

Record ocean heat has contributed to NOAA’s outlook for an above-normal 2024 Atlantic hurricane season, which extends through November 30. The historical peak of Atlantic hurricane season activity is September 10.

NOAA’s National Hurricane Center monitors current conditions and provides multi-day outlooks. Their Hurricane Preparedness hub has safety information and resources to help communities stay safe before, during, and after hurricanes.

Reporting resources on climate change and hurricanes: 

• Warm oceans fuel stronger hurricanes. Climate Central’s new Climate Shift Index: Ocean measures the influence of climate change on global sea surface temperatures every day. 

• NOAA regularly updates a summary of the science on Global Warming and Hurricanes and offers a hurricane season Media Resource Guide. 

• Climate Central’s Extreme Weather Toolkit: Tropical Cyclones provides quick facts and a collection of reporting resources on hurricanes and climate change.

Rising temperatures, falling leaves

This summer’s heat is likely to linger through fall with above-normal temperatures expected across the entire U.S. from September through November.

A warmer fall season means that the risky heat, high cooling demand, wildfires, and allergies of summer linger later into the year — affecting health, ecosystems, and the economy.

This year is not an exception. It’s part of a longer warming trend. As the entire planet has warmed since the 1890s, all four seasons have also warmed in the U.S. 

To understand how these warming trends affect local conditions, Climate Central analyzed the last 54 years (1970–2023) of fall (September, October, November) temperature data in 242 U.S. cities (see Methodology).

Fall is heating up everywhere — especially in the Southwest.

Fall temperatures have increased by 2.4°F on average across the contiguous U.S. since 1970. 

Fall warming has been universal across the contiguous U.S., but the Southwest and Northern Rockies and Plains regions have experienced the most fall warming since 1970. 

Fall is warming in 234 U.S. cities

Average fall temperatures have increased since 1970 in 234 (97%) of the 242 locations analyzed. 

• The fall season warmed by 2.5°F on average across those 234 locations. 

• More than one-third (84) of those locations warmed by 3°F or more since 1970. 

The top five fall warming locations were: Reno, Nev. (7.7°F); El Paso, Texas (6.1°F); Las Vegas, Nev. (6.1°F); Tucson, Ariz. (5.6°F); and Phoenix, Ariz (5.4°F). 

More hotter-than-normal fall days in 233 U.S. cities

The warming season is also reflected in the number of additional fall days with temperatures that exceeded the 1991-2020 normal for the season and location. 

Since 1970, 233 (96%) of the locations analyzed have seen an increase in the annual number of days above their 1991–2020 fall normal temperature. 

Eight in every 10 locations analyzed (192, or 80%) now experience at least one more week worth of warmer-than-normal fall days than they did in 1970. 

Some 97 cities now experience at least two more weeks worth of above-normal fall days than in 1970. 

And 10 locations now experience 30 or more fall days above normal than in 1970. These top locations were in Nevada, Texas, Arizona, New Mexico, Florida, and California.

Fall warming affects health, wildfire, agriculture, and more

When summer heat lingers into fall, it can extend the health risks to athletes from extreme heat or to weather-exposed workers from humid heat — especially in cities where the urban heat island can worsen heat exposure for millions. Those most at risk for heat-related illness include children.

An extended peak heat season brings higher cooling demand. Nationwide, fall cooling degree days have increased significantly since 1970. Keeping schools cool is a growing challenge as our climate warms. When air conditioners run later into the year, energy costs and heat-trapping emissions both increase.

A warming fall also contributes to a longer and more intense fall allergy season for the millions of Americans suffering with allergies and asthma. 

Hotter falls also mean a longer wildfire season. Wildfire risk, as measured by the frequency of hot, dry, windy fire weather, is getting longer and more intense — particularly in the western U.S. Parts of Nevada, California, Utah, New Mexico, Wyoming, and Montana see at least 14 days of fall fire weather. 

Wildfire smoke combined with heat-driven stagnant air can further worsen air quality posing additional risk to human health. 

Conditions that trigger fall color are also shifting with climate change, disrupting the ecological and economic value linked to fall foliage. Fall plant cycles are complex, but our understanding of their response to climate change is growing. Learn more: Rising Temperatures, Falling Leaves.

Warming also allows disease-carrying insects such as mosquitoes to linger later into the fall. Fall warming can also disrupt the timing of ecologically important events like bird migrations, hibernation, and fruit ripening.

Warmer temperatures during both spring and fall also extend the growing season, which can benefit not only some agricultural crops — but also the pests that can reduce yields. 

Warmer growing seasons can also increase the risk of water stress in plants, especially in drought-prone regions of the West and Southwest that have experienced the most fall warming. 

LOCAL STORY ANGLES

Is climate change influencing today’s air or ocean temperatures?

Use Climate Central’s Climate Shift Index and Climate Shift Index: Ocean interactive global map tools to explore data showing the influence of climate change on air temperatures and sea surface temperatures, every day.

What’s the air quality in your local area?

AirNow, a partnership of multiple government agencies, offers a wildfire and smoke tracking map, as well as interactive air quality maps, and local resources in English and Spanish, including those focused on air quality and health. The National Allergy Bureau’s Aeroallergen Network provides station-level allergen reports across the U.S. 

FIND EXPERTS

Submit a request to SciLine from the American Association for the Advancement of Science or to the Climate Data Concierge from Columbia University. These free services rapidly connect journalists to relevant scientific experts. 

Browse maps of climate experts and services at regional NOAA, USDA, and Department of the Interior offices.  

Explore databases such as 500 Women Scientists, BIPOC Climate and Energy Justice PhDs, and Diverse Sources to find and amplify diverse expert voices. 

Reach out to your State Climate Office or the nearest Land-Grant University to connect with scientists, educators, and extension staff in your local area. 

METHODOLOGY

Average temperatures and days above normal were calculated for each fall (September, October, November) from 1970 to 2023 using data obtained from the Applied Climate Information System. Fall days above normal are defined as the number of days where the average temperature was above the 1991-2020 NOAA/NCEI climate normal for the season. 

The map of the contiguous U.S. shows the change in average fall temperatures by county since 1970 with data from NOAA/NCEI’s Climate at a Glance. Previous versions of the Climate Matters map graphic showing the change in seasonal average temperature displayed the data by climate division. Note that although Connecticut recently replaced their counties with planning regions, data for Connecticut is displayed by county because NCEI data are not yet available for Connecticut’s planning regions.

Climate Central's local analyses include 247 stations. Data summaries reported in this brief are based on linear trends for only 242 stations due to data completeness measures that were not met by five stations: Dothan, Ala.; Hattiesburg, Miss., Hazard, Ky; Twin Falls, Idaho; and Wheeling, W.Va.