Mountains that normally see their peak snowpack in March are brown this year, thanks to a spring heat dome that baked the western U.S. for much of the second half of March. That’s raising alarm bells for the fire season, which is already ramping up.
John Abatzoglu, a professor of climatology at the University of California Merced, said everything is “lining up for a potentially nasty fire season across the west… the warning signs are flashing.”
The heat wave eased over the weekend after a sustained run of temperatures 11 to 17 C above normal — with highs in the 30s and 40s for multiple days in some states.
A study released on March 20 found that a heat wave this warm would be “virtually impossible” without climate change caused by human CO2 pollution, mainly from fossil fuels.
Heat records for March were broken in more than a dozen states, rapidly melting the snow off western U.S. mountains.
Early snow-melt has been linked to a longer fire season, as it dries out the landscape and provides more time and opportunity for fires to ignite and spread, said Jared Balik, a research scientist at Western Colorado University in Gunnison, Colo.
But if the snowpack was low before an early snow-melt, that doesn’t just lead to more forest area burned. The risk of very severe fires also goes up — reducing the chance of forest regeneration after the fire, Balik found in a new study published last week.
That’s bad news, considering that as of Monday, snowpack was on track to be the lowest on record at almost every western U.S. ski destination, according to University of California Los Angeles climate scientist Daniel Swain.
And not just at ski resorts — in most of the western U.S., Abatzoglu said, snowpack is at the lowest it’s been in 20 to 30 years.
Colorado, where Balik lives, saw a record-low snowpack all winter. And as of Friday, when he spoke to CBC News, it was almost all gone. Balik said it’s the earliest he’s even seen the snow-melt ramp up in the decade he’s lived in the region, and a month to a month and a half earlier than usual.
That’s given fire season a head start in both Colorado and neighbouring Nebraska.
“Colorado is now kind of covered in the smoke from those Nebraska fires,” said Balik. As of Monday, they’d already burned more than 25,000 hectares.
Wildfires have also been reported in California. Most have been small so far and in grasslands, but Abatzoglu said they suggest that the grasses in the region are now dry enough to carry fire.
Where he is in central California, it had been over 30 C for many days, and the vegetation that was normally green in the spring was browning. “It is eerily warm,” he said on Friday. “I have had my air conditioner on for the past week.”
Balik’s research shows the conditions now could lead to far more extreme fires later.
The U.S. Department of Agriculture tracks the amount of water contained in the snowpack over the winter — which is important later in the year not just for crops, but forests.
“It provides the water that trees rely on throughout their growing season,” Balik said. Less snow means drier, more flammable trees — and more severe fires. His team demonstrated this by relating satellite measurements of snowpack to satellite measurements of forests before and after wildfires over many fire seasons.
“We were surprised that there was such a strong relationship between snowpack decline and the subsequent fire season burn severity.”
In less severe fires, he said, a blaze might just burn dead wood on the forest floor, leaving mature trees intact.
On the other hand, a severe fire in a dry forest destroys everything, including the seeds that allow forests to regrow.
“That creates an opportunity for other kinds of vegetation to invade the system and replace the forest that was there,” Balik said. It could convert the forest to grassland or scrubland, he added, changing how much carbon is stored in the landscape and impacting the availability of water and wildfire habitat.
While snowpack is seeing long-term declines due to climate change across North America, Balik said, “It’s not all doom and gloom… every winter is another opportunity to acquire snowpack.”
Climate change may lead to more low-snow years, but weather patterns such as El Niño and La Niña do bring snowy winters from time to time, the study found.
And those years, Balik said, are an “excellent opportunity to do prescribed burning.” That can reduce the amount of fuels available to wildfires, reducing their severity, and such deliberately set fires are easier to control and contain in wetter years.
Hossein Bonakdari, a University of Ottawa professor, recently used satellite and drought data to look at the factors behind the severe wildfires that ravaged more than 8,000 square kilometres in Manitoba last May and how they might be predicted.
That happened after unusually lower snow cover that led to an early loss of snow, and an early heat wave that brought record temperatures of up to 37 C to Winnipeg in May.
It’s wildfire season. How can you prepare?
Bonakdari said in Canada, like in the U.S., low snowpack is a big risk factor for wildfires, especially in the west. However, he added that other factors, such as overall heat and drought, can be more important in the boreal forest.
Bonakdari said there have been drought conditions across much of Canada for the past few years, and with unusually hot temperatures expected in 2026 due to El Niño, many parts of Canada are still at risk of a severe fire season, even though the recent U.S. heat wave didn’t make it across the border.
Meanwhile, in the U.S., Abatzoglu is concerned about how widespread the heat wave — and hence growing fire risk — has been.
“It’s essentially the entire swath of [the] western U.S.,” he said. This makes it unlikely that states will be able to borrow firefighting resources from other areas.
But Abatzoglu said it’s not too late for the risk to change: “I’m hoping for April showers.”
