Sometimes the absence of something can make a bigger impact than its presence. For the summer of 2019 in Oregon — a time of year marked recently by blankets of smoke, warnings about unhealthy air, and evacuation notices — that absence came as a literal breath of fresh air.

In 2017, more than 1.1 million acres were scorched by wildfire in Oregon and Washington. 2018 was even worse, with 1.3 million acres of forest and fields going up in flame. That’s an area close to the size of Delaware up in smoke each year.

This year was a much different story: Just over 200,000 acres were scorched across both states, a nearly 84 percent drop from the two previous years.

“Our weather was closer to what weather typically looks like in Oregon and Washington,” said John Saltenberger, fire weather program manager, Northwest Interagency Coordination Center, which coordinates firefighting resources for Oregon and Washington. He noted that 2019 wasn’t exceptionally cool or wet, just that our last few fire seasons had seen temperatures well above average.

“Our expectations have become a bit warped,” he said.

The mild wildfire season saved Northwest firefighting agencies a boatload of money, too. Fighting wildfires cost Oregon and Washington more than a $1 billion in 2017 and 2018 combined, according to the Northwest Interagency Coordination Center. In 2019, both states spent less than $100 million, a 92 percent drop in costs.

Calm conditions, aggressive attack

Much of the quiet season can be attributed to weather. The relatively cool temperatures kept fuels in forests and grasslands from drying into the tinderboxes they were in recent years. Temperatures remained lower than in 2017 and 2018, and humidity stayed high enough to keep fuels moist. Lightning, when it did come through, was often followed by rain.

Fire experts measure fire danger in a number of ways, including temperature, humidity, wind speed, sunlight, and how much fuel is on the landscape. One of those measurements is called Energy Release Component, essentially the amount of energy that will be released when fuels burn. Because of the weather, Saltenberger said, that number stayed low for much of the summer.

The number of fires that started weren’t that much lower this year than last — 3,038 compared to 3,914 — but the lower potential for explosive growth meant they didn’t spread nearly as fast. Smaller fires demand fewer resources, leaving more firefighters free to position themselves around the state, able to jump into action more quickly and get to new starts before they grew.

“We saw very fast initial attack,” said Bobbi Doan, a spokeswoman for the Oregon Department of Forestry, the agency charged with fighting fires on state land. “We had lightning touch every part of the state, but we had crews prepositioned to get to fires quickly.”

The shortest season in 20 years

The start and end of fire season in Oregon is declared district-by-district, depending on fuel conditions. The Southwest Oregon District, covering Josephine and Jackson counties, was the last district to see conditions ripe for wildfire. With the arrival of rain, cooler temperatures and shorter days, officials there declared the season over on Tuesday, according to the state.

At just 99 days, it was about three weeks shorter than the average fire season, the agency said, and the shortest season they’ve seen since the turn of the century.

That’s not to say the state was bereft of blazes in 2019. The Milepost 97 Fire was sparked by an illegal campfire on July 24, and quickly grew to more than 10,000 acres. Given its proximity to Interstate 5, the conflagration produced dramatic pictures as motorists and slowed traffic, at one point jumping the highway and burning through brush on both sides of the interstate. Hundreds were evacuated and the fire burned more than 13,000 acres before full containment was announced about three weeks after the initial spark.

The biggest fire in the state this year was much less visible. The Poker Fire, which was sparked by lightning on Aug. 15, burned more than 23,000 acres in Southern Oregon before it was fully contained in late September.

The calm conditions even allowed firefighters to let some fires burn. In Eastern Oregon, the strategy on the Granite Gulch Fire in the Eagle Cap Wilderness was changed from suppression to management, as the Statesman Journal first reported. Letting the fire burn come with risks, it can cause smoke and there’s always a chance it could escape the boundaries firefighters set up, but if its managed effectively, it helps restore forest health and when fire passes through the area again, the area that burned this year will be less likely to roar into an uncontrollable blaze.

With the end of the official fire season, fire restrictions were lifted across the state, letting property owners burn debris piles and loosening restrictions on certain kinds of equipment that can start fires. It also means firefighting agencies can now focus their attention on fire prevention, conducting controlled burns where conditions allow, removing dead vegetation and helping landowners create defensible space around their homes.

A reprieve with a note of caution

State officials note that conditions can change quickly and, even with the fire season declared over, it only takes an errant spark to turn a quiet forest into a raging inferno. Authorities also note that individual fire departments have different rules about when and how the public can burn debris and it is important to check with local agencies. Still, all the safety tips that apply during the hot, dry months of the summer don’t expire with the first rains of fall.

While 2019 did provide a reprieve from the smoke-choked summers of the last few years, Doan said it was not indicative of what the future holds.

“We know better than to expect this next year,” she said. “The trends all tell us otherwise.”

And the cautionary note applies on a longer timescale as well, according to John Abatzoglou, a climatologist in the Department of Geography at the University of Idaho, where he has studied the link between climate change and wildfire extensively.

Experts have long predicted that wildfires will grow longer, more intense and more destructive as the climate continues to warm. The trend towards more-severe fire seasons is not undone by one calm year, Abatzoglou said.

“It was definitely a very quiet season across the entire western United States. There were a few large fires, but we avoided the long campaign fires that impact communities,” he said. “We know that under aggressive changes in climate we’ll still have years that have fuels that are not receptive to burning. Variability will always play a role. This one year does not refute the notion that fire seasons are getting longer.”

When the bad years do come, experts say it will be the most vulnerable — homeless people who have no shelter from smoke, or those who are disabled and unable to evacuate on their own — who will pay the highest price.

-- Kale Williams

kwilliams@oregonian.com

503-294-4048

@sfkale

Visit subscription.oregonlive.com/newsletters to get Oregonian/OregonLive journalism delivered to your email inbox.