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| Western United States heat wave | |
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| Name | Western United States heat wave |
Western United States heat wave
A prolonged episode of extreme temperatures affected the western United States, producing record highs across multiple states and straining infrastructure, health systems, and ecosystems. The event intersected with ongoing regional drought, wildfire seasons, and urban heat challenges, prompting coordinated responses from federal, state, and local entities. Scientific analyses linked the anomaly to large-scale atmospheric patterns and anthropogenic climate change, while operational agencies issued heat warnings and emergency measures.
The heat wave occurred against a backdrop of long-term warming documented by National Oceanic and Atmospheric Administration, National Aeronautics and Space Administration, Intergovernmental Panel on Climate Change, United States Geological Survey, and regional centers such as the Western Regional Climate Center. Observed trends from Scripps Institution of Oceanography, University of California, Berkeley, Stanford University, University of Washington, and Oregon State University indicated increasing frequency of extreme heat events across the Pacific Northwest, California, Nevada, Arizona, and New Mexico. Historical analogs include the 1936 North American heat wave and the 2013–2014 North American cold wave contrasts cited by researchers at NOAA National Centers for Environmental Information, Princeton University, Columbia University, and Harvard University. Measurements from Reno–Tahoe International Airport, Los Angeles International Airport, Phoenix Sky Harbor International Airport, Seattle–Tacoma International Airport, and Denver International Airport illustrated departures from climatological normals compiled by National Weather Service forecast offices and Climate Prediction Center products.
The episode unfolded over weeks with notable peaks recorded in June 2024, July 2024, and intermittent persistence into August 2024, impacting regions from Alaska's southeast coast through the Baja California Peninsula and inland to the Rocky Mountains and Great Basin. Cities reporting all-time or multi-decade records included Los Angeles, San Diego, San Francisco, Sacramento, Portland, Oregon, Seattle, Boise, Idaho, Las Vegas, Phoenix, Arizona, Tucson, Arizona, Albuquerque, New Mexico, and Denver. Rural and tribal areas such as Navajo Nation, Gila River Indian Community, Yakama Nation, and Hopi Reservation experienced acute impacts alongside national parks like Yosemite National Park, Grand Canyon National Park, Yellowstone National Park, and Mount Rainier National Park. Transportation hubs including Amtrak, Union Pacific Railroad, Burlington Northern Santa Fe Railway, and major highways such as Interstate 5, Interstate 10, and Interstate 80 reported heat-related disruptions.
Meteorologists at National Weather Service, National Hurricane Center, European Centre for Medium-Range Weather Forecasts, Weather Prediction Center, and research groups at NOAA Geophysical Fluid Dynamics Laboratory attributed the event to a persistent upper-level ridge, or "heat dome", reinforced by blocked flow linked to a downstream trough near Greenland and amplified by Rossby wave patterns studied at Massachusetts Institute of Technology and University of Colorado Boulder. Sea surface temperature anomalies in the Northeast Pacific Ocean, including a persistent warm pool similar to the Blob (ocean phenomenon), and tropical Pacific variability associated with El Niño–Southern Oscillation phases influenced moisture advection and surface heating, according to analyses from NOAA Pacific Marine Environmental Laboratory and Scripps Institution of Oceanography. Observed soil moisture deficits recorded by NASA SMAP, USDA Natural Resources Conservation Service, and United States Drought Monitor exacerbated sensible heat fluxes, while stratosphere–troposphere coupling events investigated by National Center for Atmospheric Research and European Research Council teams modulated the persistence of the pattern.
Public health systems in jurisdictions under Centers for Disease Control and Prevention guidance, including county health departments in Los Angeles County, Maricopa County, King County, Multnomah County, and Clark County, Nevada, reported increases in heat-related emergency department visits and mortality, monitored by National Center for Health Statistics and academic partners at Johns Hopkins University and University of California, San Francisco. Energy infrastructure managed by California Independent System Operator, Arizona Public Service, Bonneville Power Administration, and Nevada Power Company faced record demand and rolling outages; water utilities such as Metropolitan Water District of Southern California, Salt River Project, and Portland Water Bureau issued conservation notices. Agricultural losses affected producers represented by California Farm Bureau Federation, Arizona Farm Bureau, and United States Department of Agriculture programs, with impacts on crops like almonds, grapes, lettuce, and citrus documented by University of California Cooperative Extension and USDA National Agricultural Statistics Service. Wildfire ignitions and extreme fire behavior involved agencies including United States Forest Service, Bureau of Land Management, National Interagency Fire Center, and state fire departments, threatening communities and prompting evacuations coordinated with Federal Emergency Management Agency and state emergency management agencies. Ecosystems and wildlife in Sierra Nevada, Cascade Range, Sonoran Desert, and coastal estuaries experienced heat stress measured by researchers at Long-term Ecological Research Network sites and conservation groups like The Nature Conservancy.
Authorities implemented heat action plans drawing on guidance from Centers for Disease Control and Prevention, World Health Organization, and non-governmental groups such as American Red Cross and American Medical Association. Cooling centers were activated by city governments in Los Angeles, Phoenix, San Francisco, Portland, Oregon, and tribal governments on Navajo Nation lands, often coordinated with transit agencies like Metropolitan Transportation Authority (Los Angeles County) and Valley Metro. Grid operators deployed demand response and energy conservation measures with utilities including Pacific Gas and Electric Company, Southern California Edison, and Tucson Electric Power; federal relief funds were mobilized through Federal Emergency Management Agency programs and state-level emergency declarations by governors of California, Arizona, Oregon, Nevada, and Washington. Long-term mitigation discussions involved planners at Metropolitan Transportation Commission (San Francisco Bay Area), California Energy Commission, Arizona Department of Environmental Quality, and academic centers such as Energy Policy Institute and Lawrence Berkeley National Laboratory exploring urban heat island mitigation, building codes, and resilience finance mechanisms.
Attribution studies led by teams at World Weather Attribution, NOAA Climate Program Office, Imperial College London, Columbia University's Lamont-Doherty Earth Observatory, ETH Zurich, and Lawrence Livermore National Laboratory used observational datasets from Global Historical Climatology Network, reanalyses like ERA5, and climate model ensembles including CMIP6 and high-resolution regional models to quantify the role of anthropogenic forcing. Preliminary results commonly reported that human-induced greenhouse gas concentrations represented by datasets from Global Carbon Project increased the probability and intensity of extreme heat in the region, consistent with findings from the Intergovernmental Panel on Climate Change and peer-reviewed studies in journals such as Nature Climate Change, Geophysical Research Letters, and Proceedings of the National Academy of Sciences. Ongoing work by National Center for Atmospheric Research, Princeton University, and University of Oxford aims to refine event-specific attribution, fingerprinting techniques, and projections for future compound extremes involving heat, drought, and wildfire.
Category:Heat waves in the United States