Climate change is contributing to a growing wildfire threat in the West, but people in the East may be overlooking the risks in their own backyards.

Last year, more than 7.5 million acres — which is nearly equal to the size of Maryland — burned across the U.S., according to the National Interagency Fire Center. So far this year, nearly half a million acres have already burned. In the East, Jimmy's Waterhole Fire in New Jersey and the Owings Mills Fire in Maryland, both in April, burned close to populated areas. Currently, there are six large fires burning: two in Florida, one in Massachusetts, two in North Carolina — including the Great Lakes Fire that has burned over 32,000 acres — and another in New Mexico.

Low humidity, high temperatures and high winds combine to make it easier for wildfires to start and spread. Fire weather days have multiplied in the West, by weeks or even months in some areas. The trends in the eastern half of the country are more subtle, but risks are rising in places where wildfires can threaten population centers. These are key takeaways from research that my organization, Climate Central, recently conducted on nationwide trends in fire weather.

Courtesy of Climate Central

Seasonality is a big part of the difference. Over the past 50 years, Western fire seasons have started earlier and lasted longer, but generally summer and fall see the highest risks. That’s when low humidity and high temperatures dry out the landscape, turning spring growth into fuel and making forests more flammable, and when there are flames, high wind will spread the fire.

In other parts of the country, summers tend to be wetter and more humid, which can reduce the chances of wildfires sparking and growing. Cooler temperatures also reduce risks, so fire weather days are far less common outside the West — but so are open spaces, and that presents a different wildfire problem.

Compared to the West, the East tends to be densely populated. There may be fewer fire days, but far more people live in harm’s way, especially along the East Coast. The area where development meets undeveloped land is called the wildland-urban interface (WUI), and in the East, there are 28 million homes there — almost double the 16 million in the West —according to 2020 Census data.

The Mosquito Fire Burns In The Sierra Nevada Mountains Forcing Thousands To Evacuate
Eric Thayer/Getty Images

No state has more homes in the WUI than California’s 5.1 million. Texas ranks a distant second with 3.2 million, but after that, nine of the next 10 states are in the East, led by Florida (2.6 million) and North Carolina (2.1 million). The four leading states have also added the most homes to the WUI since 1990 — in that order — led by California (1.5 million), Texas (1.4 million) and Florida (1.3 million). From years of data, we now see a clear trend: People are moving toward wildlands and toward wildfire risk.

Florida sees more annual fire weather days on average than any other Eastern state: four of its seven climate divisions experience at least 21 days of fire-conducive conditions per year, which is triple the average across the East. Climate divisions are areas designated by National Oceanic and Atmospheric Administration within states, with broadly similar characteristics.

New residents in Florida’s WUI have moved to one of the most fire-friendly climates in the Eastern U.S., but the number of fire days there hasn’t changed much in 50 years.

North Carolina is a different story. Since 1973, three of its climate divisions now see at least eight more days of fire weather per year, led by the Northern Piedmont division along the Virginia border (more than 13 days) — the biggest increase in the East.

The next-highest increases were in even more populous areas: New Jersey’s Northern climate division (more than 10 days), including part of the New York metropolitan area, and New York’s Coastal division (more than 10 days), which includes New York City.

This doesn’t mean Manhattan faces the same risks as surrounding areas, of course. But the East overall has more land and more people in the WUI, including communities near big cities. Making the situation even worse: These communities may be less prepared to respond to fires because the threat is still unfamiliar, even to longtime residents.

Residents in the West are no strangers to the threat of fire. There are more than 31 days of fire weather annually in 36 Western climate divisions across 11 states. Among the 36 divisions,15 see more than 60 days of fire-friendly conditions, on average.

Of the 95 climate divisions across all Western states, 79 now see more fire weather days than they did 50 years ago, with nearly half (43 divisions) seeing increases of at least 14 fire days, and 20% (19 divisions) now see at least 31 more days of fire weather. Statistically, wildfire is still a predominantly Western story, and risks keep trending upward.

Of the three factors that contribute to fire weather, relative humidity — and its interaction with heat — plays a pivotal role that helps to explain why the West faces higher weather-related risks.

  • First, the West has trended drier overall as temperatures have climbed. As drought conditions persist, the already depleted moisture in soils and plants are drawn out by hot, dry air. In recent years, fire-prone areas have been parched even before summer begins.
  • Second, especially nighttime humidity levels have trended downward as temperatures have risen. That limits the natural system’s ability to recover moisture lost during the day, further boosting susceptibility to wildfire. When fires start, it also changes their behavior, which used to slow on damper, cooler nights. Without those conditions, fires can remain active and grow overnight.

Last winter’s record-setting snowpack and rain might help buck the long-term trend for earlier fire seasons in the West, but it doesn’t necessarily reduce overall risks.

For now, there’s more moisture in many historically fire-prone areas, but there’s also more new growth. If recent trends toward hot, dry conditions continue this summer, all that new growth could wither, becoming unusually abundant fuel for late-season fires. That might make 2023 yet another risky year for the growing number of people living next to wildlands in the West.

If there’s a silver lining to the rising wildfire risks in the West, it’s preparation. As conditions continue to increase the potential danger to residents, many communities are raising awareness, developing communications plans and helping people understand and manage wildfire risks.

As those risks extend eastward, local planners can model their Western counterparts to educate and protect people who haven’t had to think about wildfires until recently.

Ultimately, this research shows how the U.S. has been on a collision course with wildfire risk for decades. As climate change has elevated weather-related risks, more Americans are moving into fire-prone places, and more places are becoming fire-prone.

Just as with climate change, the most practical immediate solution is to learn about the dangers, prepare for the impacts and plan for a riskier future. Just as with climate change, the only long-term solution is to address the root causes, cut emissions to slow and ultimately stop global warming — and reduce these risks in the future.

Kaitlyn Trudeau is a senior research associate at Climate Central, a climate science nonprofit organization that analyzes and researches climate-related issues. Her research includes analyzing atmospheric influences on Western wildfire risk. She has a B.A. in physical geography from California State University, Sacramento and a M.S. in geography from the University of Nevada, Reno, where her research focused on climate change in the Arctic region.

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