On Wednesday, the governors of California and Nevada planned to tour the state line area blackened by one of two massive wildfires that have destroyed dozens of homes in the United States’ West.

Cooler weather and even some rain aided in the battle against some of the largest fires, but fire officials warned that hotter, drier weather would return later in the week, potentially posing a threat of renewed fire ferocity.

California Gov. Gavin Newsom and Nevada Gov. Steve Sisolak, both Democrats, planned a brief tour of the Tamarack Fire damage south of Lake Tahoe in the morning. The 106-square-mile (275-square-kilometer) fire was consuming timber, grass, and sagebrush, but it was more than halfway surrounded by fire breaks. Since the fire was started by lightning on July 4, at least 23 buildings have burned.

Early this week, evacuation orders for approximately 2,000 residents on both sides of the state line were lifted.

Thunderstorms brought rain and cooler, more humid weather on Tuesday, making grass and brushy areas less prone to fire, according to fire officials. Thunderstorms with some rain, possibly heavy at times, were expected to persist through Friday. “This wet stuff fell out of the sky yesterday that I barely remembered and recognized,” Dan Dallas, an incident commander for the fire, said at a press conference Tuesday evening.

It fell gently over the entire fire overnight, reducing the ferocity of the blaze in tandem with firefighter efforts.

“We are not engaging in hand-to-hand combat” on the fire, he said.

It was a welcome respite from the fiercely dry, hot weather that had scorched much of the West only a week or two earlier, when flames raged through a dozen states on bone-dry fuel. A historic drought and recent heat waves linked to climate change have made fighting wildfires in the American West more difficult. Climate change, according to scientists, has made the region much warmer and drier in the last 30 years and will continue to make weather more extreme and wildfires more frequent and destructive.

The Dixie Fire, California’s largest fire, continued to threaten more than 10,000 homes in the region about 175 miles (282 kilometers) northeast of San Francisco.

More than 325 square miles (842 square kilometers) of land had been scorched by the fire, an area larger than New York City. Weather conditions trapped smoke over the fire, and the shade helped keep temperatures and humidity high, but authorities warned that temperatures could rise to well above normal in the second half of the week.

According to Nick Truax, an incident commander for the fire, teams reviewing damage from the fire in Northern California’s mountains have so far counted 36 structures destroyed and seven damaged in the remote community of Indian Falls. It’s unclear whether that figure includes homes or smaller structures.

In neighboring Oregon, rain fell Tuesday morning on the Bootleg Fire, which has destroyed 161 homes, 247 outbuildings, and 342 vehicles in Klamath and Lake counties over the past three weeks. Crews hoped for a break from cooler temperatures and the possibility of isolated thunderstorms through Wednesday before hotter, drier weather returned, according to officials.

After scorching nearly 641 square miles (1,660 square kilometers) of remote land, crews had the lightning-caused fire more than halfway contained.

According to scientists, on July 18, a day of particularly high fire activity, the blaze spawned a fire tornado in the Fremont-Winema National Forest. According to Bruno Rodriguez, a meteorologist assigned to the Bootleg Fire, the phenomenon occurred when smoke rose nearly 6 miles (10 kilometers) into the sky and formed giant clouds.

According to Neil Lareau, an atmospheric science professor at the University of Nevada, extensive tree damage, scoured road surfaces, and soil damage indicated wind speeds ranging from 111 mph (178 kph) to 135 mph (217 kph).

“There had only been two well-documented tornado-strength vortices generated by fires prior to last year,” said Lareau, who began researching the phenomenon after fire-generated tornadoes occurred last fall. “We could not have imagined this a decade ago. However, here we are.”

Nearly 80 large, active wildfires that have blackened over 2,300 square miles (6,000 square kilometers) of land in 11 Western states and Alaska have raged on, according to the National Interagency Fire Center.

On Tuesday, the northern Rockies experienced record-breaking heat, while smoke from dozens of large wildfires as far away as California pushed pollution to unhealthy levels.

According to data from U.S. government air monitoring stations, unhealthy air was recorded around most of Montana’s larger cities, including Billings, Butte, Bozeman, and Missoula, as well as portions of northern Wyoming and eastern Idaho.