More Extreme Heat in National Parks

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KEY CONCEPTS

• The National Parks System had a record 331.9 million visitors in 2024. These treasured sites are also warming twice as fast as the U.S. as a whole. 

• The 25 most-visited national parks in the contiguous U.S. — and their 77 million visitors — are likely to experience more extreme heat in the future as human-caused climate change further warms the planet.

• According to data from the National Park Service, these 25 parks are likely to experience nearly five times more extremely hot days per year by 2050 compared to the recent past (1979-2012). 

• The increase in extreme heat by 2050 could be twice as high at the upper end of the scenarios assessed by the National Park Service. 

• The park service is adapting to both climate change and record-breaking visitation to ensure public safety and the resilience of parks’ cultural and ecological resources.

This Climate Matters analysis is based on open-access data from the National Park Service. See Methodology for details.

Warming climate, warming parks

National Park Week kicks off on April 19, when park entrance fees will be waived. The entire week is about exploring and celebrating the more than 400 treasured sites across the National Park System.

Among these, the 63 national parks are the most iconic and popular, hosting over 94 million (28%) of the record total 331.9 million visitors across the entire National Park System in 2024. Recreation visits last year peaked in July — the hottest time of year for much of the U.S. 

As our climate warms due to heat-trapping pollution, national parks are warming too, putting their invaluable cultural, ecological, geologic, and educational resources — and their millions of visitors — at risk. 

In fact, the combined area of the National Park System has warmed twice as fast as the U.S. as a whole from 1895 to 2010 — reflecting that much of the total park area is located in environments that are especially sensitive to climate change, including the Arctic, mountains, and arid regions.

As park managers decide how to adapt park operations to our changing climate, they look to scientific assessments to understand how climate change is likely to alter conditions in each park.

A hotter future in every national park

In 2024, the National Park Service published a set of reports assessing how average temperatures, heat and precipitation extremes, and drought are likely to change in each park over the coming decades. 

The reports analyze a range of future scenarios for each park to guide planning and adaptation efforts on the ground (see Methodology for details). 

The assessments find that all 63 national parks will continue to warm into the future — leading to more extreme heat. 

Here, an extremely hot day is defined as having a maximum temperature above the historical (1979-2012) 99th percentile. In other words, an extremely hot day is at least as hot as the hottest 1% of all days experienced in that park during the recent past.

According to data from the National Park Service reports, the 25 most-visited national parks in the contiguous U.S. — with more than 77 million visitors — are likely to experience a nearly five-fold increase, on average, in extremely hot days per year by 2050 compared to the recent past (1979-2012). 

• By 2050, these 25 parks are likely to experience between six and 22 more extremely hot days per year than in the recent past.  

• Among these 25 parks, Yosemite National Park is projected to experience the largest increase: a 7-fold increase from an average of four extremely hot days per year in the recent past to 26 days by 2050. 

• The most-visited national park, Great Smoky Mountains National Park, hosted more than 12 million visitors last year and is expected to experience 23 extremely hot days annually by 2050, compared to three days in the recent past (a nearly 7-fold increase). 

• Six of these 25 parks have an extremely hot day temperature threshold over 100°F: Hot Springs, Canyonlands, Joshua Tree, Grand Canyon, Arches, and Badlands. These parks are projected to experience a 3-fold to 6-fold increase in the frequency of these days by 2050. 

It’s important to note that the estimates above represent a “warm wet” scenario at the low end of the range of projected warming assessed by the National Park Service (see Methodology for details). 

• The future frequency of extreme heat could be at least twice as high at the upper range of projected warming. In a “hot dry” scenario, the 25 most-visited parks could experience a 10-fold increase, on average, in extremely hot days annually by 2050 compared to the recent past. 

Heat risks in national parks

Extreme heat is dangerous for everyone, everywhere. But especially in the national parks, where more extremely hot days can impact visitor health and safety.

Heat risks can compound for national park visitors because the parks tend to be located in extreme environments and host millions of domestic and international visitors annually, who may not be adapted (either physically or in terms of their behavior) to physical exertion and outdoor recreation in such environments. 

According to National Park Service analysis, national park visits are closely linked to temperature: 

• Visitation tends to increase during warmer months, though visits drop off when monthly average temperatures exceed about 80°F. 

• Applying these historical trends to future warming projections, the national parks are likely to see more visits each year by 2050, over a longer visitation season. 

More visits put additional pressure on warming parks and potentially put more visitors at risk of experiencing heat-related health and safety problems.

Across the 63 national parks, the weather conditions suited to safe outdoor recreation (based on wet bulb globe temperature) have become less frequent from 1984 to 2019, according to a 2024 study.

A 2023 study found that rates of heat-related illness among visitors to Grand Canyon National Park (the third-most-visited park in 2024) increased significantly with higher daily maximum temperatures. These links were strongest during the shoulder seasons (spring and fall), when visitors may not expect dangerous extreme heat that is nevertheless becoming more common. 

Extreme heat also puts wildlife, ecosystems, and infrastructure at risk across the National Park System. 

Parks responding to climate change

In response to rising heat risks, Grand Canyon National Park and other parks are taking additional steps to protect visitors, such as providing water filling stations, shade structures, emergency preparedness, and informing visitors about hazards from heat and other climate-related conditions. 

The National Park Service Climate Change Response Strategy is the foundation for park-specific efforts to understand how climate change affects parks, adapt to those changes, mitigate the root causes, and communicate the effects to the public. 

The National Park Service is already adapting to current and expected future changes brought by warming. Documented examples of changes due mainly to human-caused climate change include:

• expansion of wildfire-burned area in Yosemite National Park

• melting glaciers in Glacier Bay National Park

• increased tree mortality in Sequoia National Park

• loss of bird species in Death Valley National Park

Park-specific adaptation planning is informed by science-based scenarios covering the range of conditions that individual parks could experience in a warmer future. 

These adaptation plans aim to promote ecosystem resilience, preserve cultural heritage, and protect critical facilities and infrastructure. 

Future warming choices for national parks

Beyond adapting to current and future change, rapidly reducing heat-trapping pollution is ultimately the most impactful action to slow the rate of warming and ease mounting stress on park resources and visitors. 

According to a 2022 Climate Central analysis, the choices we make during this decade could lead to very different outcomes for parks.

By 2100, annual average temperatures across 62 national parks could warm between 5.5°F and 11.0°F compared to the 1991-2020 baseline — depending on how quickly we reduce heat-trapping pollution.

These levels of warming mean that future generations could inherit national parks that are altogether different from those enjoyed today.

LOCAL STORY ANGLES

What other climate risks are national parks facing?

With over 400 park units across the National Park Service, parks are facing a wide range of climate risks. 

• The Park-specific Climate Futures reports published by the National Park Service in 2024 include summary reports for all national parks in the contiguous U.S. Each report covers historical trends and projected future changes in temperature and precipitation (annual averages and extremes), drought, invasive species, phenology, and more. 

• Current and future climate risks in parks are discussed in a comprehensive 2021 analysis of climate vulnerability across the entire National Park System. 

• A 2020 publication reviews examples of past and anticipated future climate impacts in national parks, including: glacial melt, snow cover reduction, drought, wildfire increase, tree mortality, biome shifts, sea level rise, ocean warming and acidification, species loss, and wildlife shifts.

• Documented climate impacts and future vulnerabilities in national parks include: changes in visitation, drought or heavy rain, vulnerable infrastructure, seasonal shifts, coastal and soil erosion, habitat degradation, ocean acidification, flood risk, poor air quality, and invasive species. 

How are national parks adapting to climate change?

The National Park Service uses scenario planning to prepare for a range of likely future conditions in parks. For more information on scenario planning and examples of it in action at individual parks, check out the Climate Change Scenario Planning Showcase. Strategic decision-making about the future of park resources is also informed by the resist–accept–direct framework.

​​The National Park Service also includes 18 Research Learning Centers across the U.S. that support scientific research, education, and science-based visitor experiences. The National Park Service also manages a range of datasets, maps, publications, and other resources to support the science of our changing parks. 

CONTACT EXPERTS

Patrick Gonzalez, Ph.D.
currently: Associate Adjunct Professor, University of California, Berkeley
formerly: Principal Climate Change Scientist, U.S. National Park Service
Related expertise: climate change observed impacts, projected risks, and carbon solutions in U.S. national parks
Contact: patrickgonzalez@berkeley.edu

Christopher Craig, Ph.D.
Associate Professor
Murray State University
Related expertise: weather-related safety in national parks
Contact: ccraig8@murraystate.edu

Erin Seekamp, Ph.D.
Goodnight Distinguished Professor in Coastal Resilience and Sustainability
Executive Director, NC State Climate and Sustainability Academy
North Carolina State University
Related expertise: Climate adaptation planning
Contact: elseekam@ncsu.edu

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. 

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

Visitation data for national parks in 2024 refers to recreation visits and comes from the National Park Service Visitor Use Statistics Program and can be accessed through the Integrated Resource Management Applications (IRMA) Portal.

The historical (1979-2012) and projected future (2050) frequency of extremely hot days in national parks (in the contiguous U.S.) are from the Park-specific Climate Futures reports published by the National Park Service Climate Change Response Program in 2024. 

A methods report (Runyon et al., 2024) describes the analytical approach in detail. This Climate Matters brief refers to 2050 projections for the “warm wet” and “hot dry” climate futures scenarios, using the quadrant-average approach described in Runyon et al. (2024). The “warm wet” and “hot dry” scenarios are two of the four total divergent scenarios assessed in the Park-specific Climate Futures reports and used for scenario-based adaptation in parks. Across the national parks, the “warm wet” scenario generally represents the lower end of projected average warming and extreme heat frequencies. The “hot dry” scenario generally represents the upper end of these projections. 

Note that the Park-specific Climate Futures reports use CMIP5 data (see Runyon et al., 2024 and FAQs for details). The park-specific 2022 Climate Central analysis cited in this brief uses CMIP6 data (see linked brief for detailed methodology).