Wildfires That Tend To ‘Sleep’ At Night. Climate Change Made Them Hotter More Time

Yves here. To see what the US has in store for the future. look for severe, long-lasting fires in northern Thailand (Chiang Mai) and Laos. From last weekend’s South China Morning Post, on ‘The worst I’ve ever seen’: forest fires raging across Thailand, in the Mekong region:

Forest fires raging in Laos, Myanmar and Thailand have engulfed large areas in noxious smoke, leaving exhausted firefighters battling the blazes and smog-dampened communities looking to the skies for rain and their governments to deal with the worsening mess every year.

The dry season fires have brought a public health crisis to northern Thailand, including Chiang Mai, and much of Laos and eastern Myanmar, as the dry forest provides hot-box conditions for wildfires.

Some fires are caused by farmers slashing and burning to clear land in a more rapid, less labor-intensive way before the planting season, especially in Laos and Myanmar, where enforcement of bans on the practice remains weak.

Thailand’s northernmost provinces of Chiang Rai, Chiang Mai and Mae Hong Son are covered in thick clouds of pollution along the Myanmar and Laotian borders.

On Sunday, Thailand recorded more than 600 fires, most of them in the north, with some coming down the western border with Myanmar. Hospitals across the country have reported an increase in patients seeking help for respiratory illnesses linked to high levels of PM2.5, the toxic particles that carry polluted air.

“The air we breathe is a basic right that everyone deserves,” Maneerat Khemawong, a senator from Chiang Rai province, told reporters on Monday. “The air condition in the northern region has been at a critical level from purple to black for more than two months … which is a trend of worsening conditions every year,” he said, as other northern MPs pressed the government to do more about the worsening pollution.

“Hot spots accumulated in neighboring countries are more than 10 thousand, and this smoke drifts to Thailand,” he said, referring to satellite data.

By Seth Borenstein, AP Science Writer. Cross posted from Yale Climate Connections

The hot season for North American wildfires is entering extra time. Flames are burning later into the night and starting early in the morning because human-caused climate change is increasing the hot and dry conditions that fuel fires, a new study found.

Fires often subsided or died out at night as temperatures dropped and humidity increased, but that doesn’t happen very often. The number of hours in North America where the weather is favorable for wildfires is 36% more than 50 years ago, according to a study published earlier this month in Science Advances.

Places like California have 550 hours that are likely to be hotter than in the mid-1970s. Parts of southwestern New Mexico and central Arizona see about 2,000 more hours a year when the weather is prone to wildfires, the highest increase seen in the study, which looked at Canada and the United States. The study looked at times when conditions were ready to burn, but that did not mean fires broke out during that entire period.

Recent Big Fires in LA and Hawaii Burned Overnight

Nighttime fires are more difficult to fight and include the Lahaina, Hawaii fire in 2023, the Jasper fire in Alberta in 2024, and the Los Angeles fires in 2025, the study said. The Maui fire broke out at 12:22 am

It’s not just a stretchy watch. A calendar too. The number of days with hot weather increased by 44 percent, effectively adding 26 days over the past half century.

Especially warm, dry nighttime weather, with little wind, the study authors said.

“Fires tend to accelerate at night, or even stop,” said study co-author Xianli Wang, a fire scientist with the Canadian Forest Service. “But under the most dangerous fire conditions, the fire burns all night or at night.”

And Wang said the warming of the Earth’s atmosphere means it’s like getting worse.

It’s Hard to Fight Fire at Night

“Non-sleeping” fires become active the next day, making them harder to put out, said University of California, Merced fire scientist John Abatzoglou, who was not part of the study, said in an email.

“Nights are not what they used to be—that is, reliable breaks for wildfires,” he added. “The widespread warmth and lack of moisture keeps the fire burning at night.”

Wildland firefighter Nicholai Allen, who also founded a firm that makes home fire prevention equipment, said it is more difficult to fight fires at night.

“You have to understand that you have snakes and bears and mountain lions and all the things you have during the day,” Allen said, noting that his colleague was bitten by a bear. But at night, they are really afraid, and they run away from the fire.

Canadian researchers analyzed nearly 9,000 large fires from 2017 to 2023 using weather satellites and other instruments to obtain hour-by-hour data on atmospheric conditions during the fire, such as humidity, temperature, wind, rain, and fuel moisture levels. They developed a computer model that correlated weather conditions with fire conditions and applied them to historical data in Canada and the United States from 1975 to 2106.

Nights Warm Up Faster Than Days
Scientists have long argued that greenhouse gases from burning coal, oil, and natural gas make nights warmer than days because of increased cloud cover that absorbs and re-radiates heat to Earth at night as a blanket. Since 1975, the combined US summer has seen minimum nighttime temperatures warm by 2.6 degrees Fahrenheit (1.4 degrees Celsius), while daytime temperatures have increased by 2.2 degrees Fahrenheit (1.2 degrees Celsius), according to the National Oceanic and Atmospheric Administration.

The humidity at night is not “reversing” from its daytime dryness as it used to, said lead study author Kaiwei Luo, a fire science researcher at the University of Alberta.

Wildfires are often accompanied by drought, especially severe drought, which means not only dry air, but hot, dry air that absorbs more moisture from the soil and vegetation, causing the fuel to burn more, Wang said. In a drought, there is often a vicious cycle of drying and when it is really dry, the warm air has more power to absorb moisture from the oil.

Just as warm nights, especially in heat waves, do not allow the body to recover, warm nights do not allow forests to recover, Wang said. It can take weeks for dead fuel to regain its lost moisture and become less flammable, he said.

“It’s just stress on the plants,” said Wang. “That increases the amount of fuel.”

From 2016 to 2025, wildfires in the United States on average burned an area the size of Massachusetts each year, just over 11,000 square miles (28,500 square kilometers). That’s 2.6 times the average area burned in the 1980s, according to the National Interagency Fire Center. Canada’s land burned on average in the past 10 years is 2.8 times greater than in the 1980s, according to the Canadian Interagency Forest Fire Centre.

Syracuse University fire scientist Jacob Bendix, who was not part of the study, called the study a sobering reminder of the role of climate change in driving “increasing fire intensity in nearly every burn-prone region of North America.”