{"id":42658,"date":"2026-06-18T07:15:00","date_gmt":"2026-06-18T14:15:00","guid":{"rendered":"https:\/\/www.lifeandnews.com\/articles\/?p=42658"},"modified":"2026-06-17T23:38:32","modified_gmt":"2026-06-18T06:38:32","slug":"heat-waves-increase-wildfire-risk-a-new-study-explains-how-much-and-its-not-a-small-number","status":"publish","type":"post","link":"https:\/\/www.lifeandnews.com\/articles\/heat-waves-increase-wildfire-risk-a-new-study-explains-how-much-and-its-not-a-small-number\/","title":{"rendered":"Heat waves increase wildfire risk \u2013 a new study explains how much, and it\u2019s not a small number"},"content":{"rendered":"\n

Dmitri Kalashnikov<\/a>, University of California, Merced<\/a><\/em>; Cong Yin<\/a>, University of California, Merced<\/a><\/em>; Madhulika Gurazada<\/a>, University of California, Merced<\/a><\/em>, and Mukesh Kumar<\/a>, University of California, Merced<\/a><\/em><\/p>\n\n\n\n

When heat waves hit the Western United States, the risk of wildfires quickly rises. The prolonged heat dries out vegetation, but that\u2019s only part of the cause \u2013 heat waves also play other roles in spreading wildfires.<\/p>\n\n\n\n

In a new study, our team<\/a> of fire<\/a> and climate<\/a> scientists<\/a> looked at two decades of wildfire activity in the West, from 2001 to 2024, and for the first time quantified the effect of heat waves on those fires<\/a>.<\/p>\n\n\n\n

We expected a big impact, but the numbers still surprised us: While heat waves, which we defined as three or more consecutive days with temperatures in the top tenth of hottest days, accounted for only 12% to 15% of warm-season days, we found that 42% of all the area burned by fires had occurred during or right after a heat wave.<\/p>\n\n\n\n

Moreover, the amount of the area that burned each day was more than 50% larger during heat waves than during the cooler days right before the heat wave began in many parts of the West. In some regions, the difference was much larger \u2013 up to 300%.<\/p>\n\n\n\n

How heat waves worsen fire risk<\/h2>\n\n\n\n

Heat waves create conditions that favor wildfire ignition and spread in a few ways.<\/p>\n\n\n\n

First, hot temperatures increase the atmosphere\u2019s demand for moisture<\/a>, meaning the rate at which the air can evaporate moisture from the land and vegetation. As a result, these fuels rapidly dry out, making them easier to ignite.<\/p>\n\n\n\n

Heat waves also limit nighttime humidity. The drier air allows fires to remain active for longer periods and burn through more hours of the night<\/a>.<\/p>\n\n\n\n

Making matters worse, heat waves can create conditions favorable for lightning because of the hot, unstable atmosphere. We found increases in cloud-to-ground lightning, including \u201cdry\u201d lightning<\/a>, during and after heat waves across many parts of the West.<\/p>\n\n\n\n

\"How
An illustration shows how heat exacerbates wildfire risk. Mukesh Kumar<\/figcaption><\/figure>\n\n\n\n

Dry lightning can occur when the precipitation in a storm system evaporates before it reaches the ground. This type of lightning is particularly dangerous because it can ignite vegetation without producing enough rainfall to douse the flames.<\/p>\n\n\n\n

These factors combine to heighten the risk of wildfires. That risk often persists even after the heat wave ends<\/a>, as dry vegetation and dead material on the ground tend to remain unusually dry for days after temperatures return closer to normal \u2013 allowing fires to continue growing.<\/p>\n\n\n\n

Trends in heat and fires<\/h2>\n\n\n\n

The connection between heat waves and wildfire activity is becoming increasingly important because heat waves are becoming more common<\/a> as global temperatures rise, fueled by greenhouse gas emissions<\/a>.<\/p>\n\n\n\n

Since 2001, the number of heat wave days across Western U.S. forests has nearly doubled. During the same period, the amount of forest area burned increased by 2.5 times<\/a>. Strikingly, without the increase in heat wave days since 2001, we found that the cumulative are of burned forest would have been 37% smaller.<\/p>\n\n\n\n

\"A
Heat waves have a bigger influence in some regions than others. The map shows the percentage of the total area burned during and immediately following heat waves from May to October, 2001-2024. Dmitri A. Kalashnikov, et al., 2026<\/a><\/figcaption><\/figure>\n\n\n\n

However, not all ecosystems respond the same way.<\/p>\n\n\n\n

While we found a strong long-term relationship between increasing heat waves and increasing burned area in forests, this was not the case in grasslands and shrublands, where the total burned area has not increased. In grasslands and shrublands, the amount of land that burns in a given year is influenced more strongly by the amount of available vegetation than by heat alone.<\/p>\n\n\n\n

\"\"
How burned area and lightning-caused wildfire ignitions increase during and after heat waves, from a review of wildfires in the Western U.S. from 2001 to 2024. The chart shows the percentage increase each day compared to levels before a heat wave. For example, on average, the seventh day after the heat wave starts produces an almost 200% increase in forest burned area compared to the conditions that existed before the heat wave. John Abatzoglou<\/figcaption><\/figure>\n\n\n\n

A future with even drier heat waves<\/h2>\n\n\n\n

Climate change is causing Western U.S. summers to trend hotter and drier<\/a>. Consequently, relative humidity during heat waves has also declined in recent decades, especially in forested regions of California, Oregon and Washington.<\/p>\n\n\n\n

These drier heat waves appear particularly effective at increasing wildfire activity. Alongside long-standing fire deficits<\/a>, which resulted from the practice of quickly extinguishing fires rather than allowing low-level fires to burn away forest debris, these factors have escalated the potential for large fires in the West.<\/p>\n\n\n\n

Wildfire forecasts already account for factors such as wind, humidity and fuel dryness, but they typically have not included heat waves. Our research suggests that heat waves deserve greater attention, as they are not just periods of uncomfortable and sometimes deadly<\/a> weather, but are also increasingly important drivers of wildfire risk.<\/p>\n\n\n\n

Dmitri Kalashnikov<\/a>, Postdoctoral Research Scholar, University of California, Merced<\/a><\/em>; Cong Yin<\/a>, Postdoctoral Researcher in Climate and Hydrology, University of California, Merced<\/a><\/em>; Madhulika Gurazada<\/a>, Ph.D. Student in Management of Complex Systems, University of California, Merced<\/a><\/em>, and Mukesh Kumar<\/a>, Postdoctoral Researcher in Wildfires and Complex Systems, University of California, Merced<\/a><\/em><\/p>\n\n\n\n

This article is republished from The Conversation<\/a> under a Creative Commons license. Read the original article<\/a>.<\/p>\n","protected":false},"excerpt":{"rendered":"

Dmitri Kalashnikov, University of California, Merced; Cong Yin, University of California, Merced; Madhulika Gurazada, University of California, Merced, and Mukesh Kumar, University of California, Merced When heat waves hit the Western United States, the risk of wildfires quickly rises. The prolonged heat dries out vegetation, but that\u2019s only part of the cause \u2013 heat waves […]<\/p>\n","protected":false},"author":56,"featured_media":42659,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[1862,42,10,118,3410],"tags":[8255,4701,4737,6698,885,891,886,860,8543,209,14704,15200,2202],"_links":{"self":[{"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/posts\/42658"}],"collection":[{"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/users\/56"}],"replies":[{"embeddable":true,"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/comments?post=42658"}],"version-history":[{"count":1,"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/posts\/42658\/revisions"}],"predecessor-version":[{"id":42660,"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/posts\/42658\/revisions\/42660"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/media\/42659"}],"wp:attachment":[{"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/media?parent=42658"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/categories?post=42658"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.lifeandnews.com\/articles\/wp-json\/wp\/v2\/tags?post=42658"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}