The first Alaska wildfire of 2016 broke out in late February, followed by a second there just eight days later.
New Mexico has had 140 fires this year, double the number in the same period last year, fueled by one of the warmest, driest winters on record.
And on the border of Arizona and California this month, helicopters dumped water on flames so intense that they jumped the Colorado River, forcing the evacuation of two recreational vehicle parks.
Fires, once largely confined to a single season, have become a continual threat in some places, burning earlier and later in the year, in the United States and abroad. They have ignited in the West during the winter and well into the fall, have arrived earlier than ever in Canada and have burned without interruption in Australia for almost 12 months.
A leading culprit is climate change. Drier winters mean less moisture on the land, and warmer springs are pulling the moisture into the air more quickly, turning shrub, brush and grass into kindling. Decades of aggressive policies that called for fires to be put out as quickly as they started have also aggravated the problem. Today’s forests are not just parched; they are overgrown.
In some areas, “we now have year-round fire seasons, and you can say it couldn’t get worse than that,” said Matt Jolly, a research ecologist for the United States Forest Service. “We expect from the changes that it can get worse.”
The 10.1 million acres that burned in the United States last year were the most since before 1960, and the top five years for acres burned since then were in the past decade. The federal costs of fighting fires rose to $2 billion last year, up from $240 million in 1985.
“We take our job to protect the public seriously, and recently, the job has become increasingly difficult due to the effects of climate change, chronic droughts and a constrained budget environment in Washington,” Tom Vilsack, the agriculture secretary, said in a statement, noting that seven firefighters died and 4,500 homes burned in wildfires in 2015.
Randi Jandt, a fire ecologist with the federally funded Alaska Fire Science Consortium, resists the term “year-round fire season” because Alaska and other places still have months with snow cover. She has adopted an alternative that she said reflects the more intense nature of recent fires.
“I’m worried about a runaway fire season,” Ms. Jandt said. The term captures the idea that dry conditions could lead to fires that simply burn out of control, she explained, as some almost did last summer, Alaska’s second-largest fire season on record, after 2004.
The issue has led to disagreements among many fire ecologists about how best to attack the problem. Some argue that fires should be left to take their natural course and clear out the thick, dry brush on the forest floor. But that approach has run into a challenge: More and more people are moving into wild lands.
Retirees and urbanites seeking more pastoral settings are pushing farther into places that firefighters must now protect. And these modern-day settlers have been supported by municipalities looking to expand their tax bases, and by technology that lets people live and work anywhere they can get an Internet connection, said Ray Rasker, the executive director of Headwaters Economics, a research organization that provides consulting services to communities and governments on fire prevention.
“It’s a wonderful new world, where I can live anywhere I want,” Mr. Rasker said, echoing an opinion he said he had often heard. “I want to live in the woods, but the woods are now flammable, much more flammable than they used to be.”
“It adds up to more people dying, more houses burning, and agencies devoting more than half of their fire budget to defending homes,” he said.
Hawaii, for example, exhausted in February the annual allocation of money it had set aside to fight wildfires, four months before the busy summer fire season. The United States Forest Service spent more than half of its entire budget on firefighting last year, at the expense of programs aimed at minimizing the risk of fires in the wild, such as planned burns of overgrown patches.
The agency finds itself caught in a troubling cycle: With budgets squeezed for treating forests to help prevent fires, it inevitably has to spend more money putting them out.
By key measures, fire season has grown significantly longer in the past 30 years. Dr. Jolly’s research shows that the season, measured by how many days are hot and dry enough to increase the likelihood of fire, has lengthened by 30 to 45 days across big patches of the United States, notably the West.
By another measure, the time between the first and last large fires in a year, the length of the season in the West has increased by 78 days since the 1970s.
Firefighters in the United States and abroad have been trying different approaches. In the Canadian provinces of Alberta and Manitoba, which recorded more than twice as many fires last year than their 25-year averages, fire season started on March 1, a month ahead of the norm.
Alaska has also moved up its fire season, defined by the date that permits are required for residential yard or other refuse burning, to April from May. Increasingly, fire crews are making calculated decisions to let fire consume the land, concentrating their efforts on safeguarding communities and watersheds — and, in turn, minimizing the risks they face.
“More and more, fire crews are pulling back, willing to sacrifice land for safety,” said Stephen J. Pyne, a professor at the School of Life Sciences at Arizona State University and one of the country’s foremost fire historians.
Firefighters and state officials also face pressure to cut costs. But while firefighters are adapting as they can, “putting their efforts where the values are higher,” as Mr. Pyne put it, states are struggling.
This year in Washington State — where a combination of drought, warm temperatures and dense forests made for a long and costly wildfire season last year — Peter Goldmark, public lands commissioner of the Department of Natural Resources, asked the State Legislature for an extra $24 million to train more firefighters, put more equipment into the hands of local fire districts and help homeowners clear brush from their properties. He got $6.7 million.
“Given the wet winter, it’s hard to persuade people we may be entering a time of hotter, drier summers, and we need to be ready,” Mr. Goldmark said.
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He is preparing for “another very difficult fire season,” he said. A large stretch of the Southwest, from Texas and New Mexico down through southern Arizona and into Nevada and California, has already been warned by national forecasters to prepare for an “above normal” risk of significant wildfires through July.
Clay Templin, fire and aviation manager for the Forest Service’s Eastern Regional Office, which covers 17 national forests from Missouri to Maine, said that parts of the territory the office oversees, such as the White Mountains in New Hampshire, are now at risk of fire. That traditionally did not happen because “there was a whole lot more snow on the ground,” he said.
Early last month, a fire broke out in the Apache-Sitgreaves National Forest in Northern Arizona, consuming about 600 acres of land that are usually moist in the winter.
“It’s too early for fire in these parts,” said James Molesa, chief deputy of the Navajo County Sheriff’s Office.
Dry grass ignited in the forest when someone — officials have not identified the person — was shooting for practice at an oxygen tank, which then exploded, sending sparks flying, Chief Deputy Molesa said.
The flames traveled along some of the same area that burned in a big fire 14 years ago, though that fire happened in June, during the state’s traditional fire season — another sign, fire officials said, of the changing conditions they face.
At the Arizona Wildfire and Incident Management Academy, where three classes of firefighters trained last month for their first season, instructors emphasized the value of a strategy known as “indirect attack,” the safest and most common method to fight today’s large, hot and volatile blazes.
The strategy calls for crews to carve a so-called fire line — buffer zones devoid of anything that burns — away from the edge of the fire, and then to burn the vegetation that stands in between, depriving the flames of the fuel that feeds them.
Dean Steward, a supervisor at the academy, said that fires were small enough 20 years ago that dirt trails, such as those used by all-terrain vehicles in the wild lands, were enough to stop them.
“Now,” Mr. Steward said, “you can put a six-lane highway between your crew and the fire and, still, the fire will jump it.”