Western Fire Weather Days Increasing

KEY CONCEPTS

• Wildfire seasons are shaped by many forces, and climate change is contributing to recent increases in wildfire intensity, frequency, and season length in the western U.S. 

• Heat, dryness, and wind—the three components of fire weather—are occurring more frequently across the western U.S. since 1973, according to new Climate Central analysis.

• Some areas are seeing more fire weather during seasons when wildfires were previously rare. New Mexico is among the states seeing the largest increases in risks during the spring.

• Large wildfires can kill people and destroy property. Utilities may shut off power during fire weather to prevent equipment-related ignitions. And smoke can affect people living thousands  of miles away, including on the East Coast. 

Fire weather conditions promote wildfires.
Fire weather refers to meteorological conditions that promote the spread of wildfires. Climate Central’s analysis focuses on three conditions fundamental to fire weather: relative humidity, temperature, and wind. 

• When relative humidity levels are very low, the air feels dry and it sucks moisture from the land, leaving vegetation dry and prone to burning. 

• Hotter temperatures have a direct influence on fire behavior, heating the fuels and making them more likely to ignite. 

• Wind supplies oxygen to a fire, causing it to burn more rapidly. Wind increases evaporation, drying out the land. Wind also carries embers, which helps fires spread.

More western fire weather days—across all seasons.
Climate Central analyzed weather station data from 225 locations across 17 western states going back to 1973. Station data were aggregated by climate division (you can find your climate division here) and fire weather trends were assessed annually and by season. 

• Parts of Texas, California, Oregon, and Washington are experiencing fire weather more than twice as often now compared with the early 1970s. 

• Parts of New Mexico, Texas, and southern California have experienced some of the largest increases in fire weather days each year.

• Areas of New Mexico are now seeing two more months of fire weather on average than in 1973—creating earlier fire seasons and fueling fires like those that have already occurred there this year.

• Some areas are also seeing more fire weather days during winter, including in northeastern New Mexico, northwestern Texas, and southern Colorado.

• Fire weather days increased more in interior regions than in coastal regions. Higher humidity levels along the coast mean these areas are less likely to reach the low relative humidity threshold used in the analysis. 

• By contrast, some parts of North Dakota, South Dakota, Kansas, and Nebraska experienced declines in the frequency of fire weather days. This is part of a region where springs and summers have been cooling slightly—likely because of the effects of agricultural practices. 

Fire weather conditions can cause far-reaching problems.
One important approach for reducing fire risk is known as “prescribed burning.” This type of managed burning can ultimately reduce fire risk, but when fire weather days are more frequent, there are fewer opportunities to safely manage prescribed burns. 

On fire weather days, power companies may shut off electricity to consumers to avoid equipment-related ignitions. Although these “public safety power shut offs” can reduce the risk of fire, they can also create unintended health and economic risks. Researchers found that the daily power needs for 12 million people were unavailable in Northern California in 2019 due to public safety power shut offs, causing estimated economic impacts of around $10 billion. 

Communities near wildfires and those far downwind are also being affected. Smoke is a dangerous pollutant that contributes to a variety of health problems, increasing susceptibility to asthma and asthma attacks. It can also make one more vulnerable to influenza and other viruses like COVID-19. Smoke poses especially high risks to those with other health problems, particularly among seniors and others with weakened lung health.

POTENTIAL LOCAL STORY ANGLES

Does your local area face immediate fire risk?
You can find daily reports of elevated fire weather conditions at NOAA’s Storm Prediction Center. The Incident Information System identifies where wildfires have been reported and provides detailed information on conditions. You can stay updated about risk of fire with the North American Seasonal Fire Assessment and Outlook, produced by the National Interagency Fire Center (NIFC) in Boise, Idaho at the beginning of each month. You can also search your locality on the Wildfire Risk to Communities website. 

Are wildfires affecting air quality in your area?
AirNow, a partnership of multiple government agencies, has a number of publications on wildfire smoke and air quality, and a wildfire and smoke tracking map. California Air Resources Board (CARB) maintains a series of interviews with experts on wildfire smoke and air quality, that are available for attribution, as well as air quality data. PurpleAir also maps air quality indexes across the country. 

What are solutions to the increasing risk of wildfires? 
A number of solutions to adapting to the risk of wildfire include increased use of land management techniques that eliminate excessive fuels, such as prescribed burns; forest thinning to remove young trees and bushes; and allowing small fires to burn themselves out when it’s safe to do so. There are also toolkits to prepare homes and create evacuation plans. But fire weather conditions will increase around the world as the planet warms. Reducing carbon pollution by aggressively switching away from fossil fuels would limit global warming and stabilize climate conditions. 

LOCAL EXPERTS 

The SciLine service, 500 Women Scientists or the press offices of local universities may be able to connect you with local scientists who have expertise on wildfires and climate change. The American Association of State Climatologists is a professional scientific organization composed of all state climatologists. 

NATIONAL EXPERTS 

• Climate and wildfires

  • John Abatzoglou **, Ph.D., Associate Professor and Graduate Program Chair (MIST)
    University of California, Merced
    jabatzoglou@ucmerced.edu

  • Daniel L. Swain **, Ph.D., Climate Scientist, Institute of the Environment & Sustainability, UCLA
    California Climate Fellow, The Nature Conservancy
    dlswain@ucla.edu

  • Karen Aline McKinnon, Ph.D., Assistant Professor,  Institute of the Environment and Sustainability, Department of Statistics, UCLA
    kmckinnon@ucla.edu

  • Josue Medellin-Azuara*, Ph.D., Associate Professor of Environmental Engineering, University of California, Merced
    jmedellin-azuara@ucmerced.edu

• Wildfire smoke and health risks

  • Colleen Reid, Ph.D., Assistant Professor of Geography, University of Colorado, Boulder
    colleen.reid@colorado.edu

  • Erin Landguth, Ph.D., Associate Professor, School of Public and Community Health Sciences, University of Montana
    erin.landguth@mso.umt.edu

*Available for interviews in Spanish and English
** Serve as science advisors for Climate Central's fire weather analyses.

METHODOLOGY

See detailed methodology in the appendix of Climate Central's 2021 report, Fire Weather.