A fire near the Grand Canyon National Park in Arizona has grown more than 20 times in size in 24 hours as an intensifying wildfire season sees the return of Canadian wildfire smoke into the U.S.

The White Sage Fire, located in Kaibab National Forest, has forced hundreds to evacuate. It has scorched over 20,000 acres and hasn’t been contained, according to authorities. Another fire nearby — the Dragon Bravo Fire — is also threatening historic buildings in the area. Meanwhile, officials warn that weather conditions aren’t favorable for containing the flames. 

Both fires are believed to have been started by lightning, according to the U.S. Forest Service.

Meanwhile, much of the Upper Midwest on Saturday was dealing with swaths of unhealthy air because of drifting smoke from Canadian wildfire.

The smoke from the Canadian wildfires is covering the northern region of the U.S. at a time when people want to be enjoying lakes, trails, and the great outdoors.

Most of Minnesota and parts of Montana, North Dakota and Wisconsin were ranked “unhealthy” for air quality on a U.S. Environmental Protection Agency map. Part of North Dakota that is home to Theodore Roosevelt National Park and other tourist attractions was ranked “very unhealthy,” some of the worst air quality in the nation.

In Minnesota, “If you have a nice pork loin you can hang from a tree, it’ll turn into ham,” quipped Al Chirpich, owner of the Hideaway Resort near Detroit Lakes, where people come to enjoy tree-lined Island Lake for fishing and other water activities.

The conditions started Friday, dragging smoke from the Canadian wildfires down to the surface, said National Weather Service Meteorologist Jennifer Ritterling, in Grand Forks. Periods of bad air quality are expected to last through the weekend in the region, she said.

Limiting time outdoors, keeping windows closed and running air purifiers are good ideas for people with lung conditions such as asthma and chronic obstructive pulmonary disease, and even healthy people, Ritterling said.

“Our summers up here are fairly short and so everyone wants to get out and enjoy them, and it’s a little frustrating when there’s this smoke in the air,” she said.

Meanwhile, all of Manitoba is under a state of emergency because of the wildfires, which have led to 12,600 people evacuating their homes in the Canadian province. The fires in the central province have burned over 3,861 square miles, the most land burned in 30 years of electronic record-keeping.

Under 1,000 people have evacuated their homes in Saskatchewan, where wildfires also continue to burn.

Forecasters and national Arizona parks officials have been issuing warnings over dangerous weather conditions in the last few days as temperatures reach over 110 degrees.

“Not only is there dangerous heat at the lower levels of the Grand Canyon, but lots of smoke and high fire danger,” NWS Flagstaff said on social media on Saturday. “Don’t mess around.”

A 67-year-old Texas man died while hiking in the Grand Canyon, the National Park Service said Wednesday.

The White Sage Fire also started Wednesday, and the Dragon Bravo Fire began on July 4, according to authorities.

More than 200 firefighters and support personnel worked to halt the uncontained fire Saturday as it burned across a high-altitude plateau between the communities of Lonesome, White Sage and Jacob Lake.

In Colorado, Black Canyon of the Gunnison National Park was closed because of a 4.4-square-mile wildfire burning on the South Rim of the park, known for its dramatic, steep cliffs. A few miles from the fire, an evacuation was ordered for the community of Bostwick Park, and a nearby highway also was shut.

The fires in and near both national parks led to evacuations of hundreds of people.

Chirpich, the Minnesota resort owner, said he has plans to go to Black Canyon of the Gunnison National Park on Thursday and is “a bit pensive about how that’s going to be there.”

“I’m going to leave one smokehouse for another, I guess,” he said.