Heavy smoke from several large wildfires blazing in Canada and Minnesota is expected to engulf large swaths of the Midwest and Northeast U.S. this week, exposing millions of people to dangerous air pollution.

Over 100 wildfires currently are burning in Canada and winds are carrying the smoke southeast. Warnings about dangerous, unhealthy air extended Wednesday from Minnesota through Toronto and into New York. Unusually hot summer temperatures were expected too.

The best advice is to stay indoors to avoid both the smoke and the extreme heat, said Tyler Hasenstein, meteorologist with the National Weather Service in Chanhassen, Minnesota.

“Those two things coinciding with each other is not good from a health perspective,” he said.

Rangers try to get thousands of campers out of remote Minnesota wilderness

In far northeastern Minnesota, rangers were trying to warn people that the Boundary Waters Canoe Area Wilderness was closed Tuesday because about 17 fires caused by lightning more than a week ago were spreading through the vast wilderness accessible primarily by canoe.

Rangers estimated anywhere from 6,000 to 10,000 people were inside the 1.1-million-acre wilderness, which is almost the size of Delaware, Superior National Forest spokesperson Joy VanDrie said.

“It’s an arduous job,” VanDrie said of rangers and campers having to canoe for hours or even carry their boats over land to evacuate.

No injuries or deaths have been reported. Rangers were going through every lake and waterway and officials estimated they had about 90% of the people out Wednesday.

Campers rescued this week said skies quickly darkened from smoke and they could feel the heat as they paddled or were taken by boat to safety.

Jan Bailey was camping with her husband, daughter, son-in-law, two grandchildren and three dogs when they noticed wispy smoke on the horizon. Two hours later, they could see a raging firestorm. A paddleboarder with a satellite phone fled to their campsite and they called forestry rangers who sent a boat to rescue them and others.

“We had fire on both sides of us at that time,” Bailey told Minnesota Public Radio. “So we’re just weaving between the lakes. It’s a little smoky. Campsites are going up.”

Even the Canadian Air Force pitched in. They rescued two groups of youth campers Wednesday who had crossed the border. One group was stuck on an isolated sandbar, Minnesota Gov. Tim Walz said.

VanDrie didn’t know when the area might reopen. Minnesota officials said some fires in the Boundary Waters will be allowed to burn indefinitely but will be monitored to ensure they don’t threaten people or property.

Severe drought and heat have led to a busy wildfire season

Dan Westervelt, associate professor at Columbia University’s Climate School, said severe drought conditions combined with heat in Canada and the U.S. have created “a perfect storm for really dry conditions to provide a lot of fuel for these wildfires to burn.” Research shows warming temperatures from burning coal, oil and gas are making fires more frequent and intense.

High levels of fine particulate matter in the air from wildfire smoke may be unhealthy for sensitive groups, such as children and people with heart or lung conditions. The particulates can cause shortness of breath, coughing, dizziness or fatigue and aggravate heart and lung diseases and other chronic health issues.

Experts suggest wearing a N95 mask if you have to be outside and keeping your indoor air cleaner by closing windows and running an air purifier or air conditioner.

It’s been a particularly busy and deadly fire season in the U.S. About four dozen large fires are currently burning across 15 states, from Minnesota and North Carolina to Colorado, Utah, Idaho, Oregon and California, according to the National Interagency Fire Center.

Prolonged drought and record-low snowpack levels combined to make conditions ripe for rapid fire growth. More than 16,800 people are assigned to fighting blazes across the county. The fires have burned over 5,678 square miles (9,138 square kilometers) — more than the size of Yellowstone and Grand Canyon national parks combined, the agency said.

Comparison view of clear vs. smoky conditions in Larsen, Wisconsin:

Smoke spreads as officials warn wildfires could burn for months

In Minnesota, officials warned large fires could burn for months. In Minneapolis, the high Wednesday was expected to be 96 degrees F and temperatures above 90 F were expected the rest of the week.

“It could well be we’re having significant fires throughout the summer until we have snow. Snow would be a good thing,” said Patty Thielen, director of the state Department of Natural Resources.

Officials in Michigan and Wisconsin warned residents about air quality issues that could last for days and the problems extended even to Maine, where residents were reporting a yellowish and brownish color in the sky.

The most intense smoke could spread as far south as Washington, D.C., by midday Thursday.

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Associated Press writers Susan Montoya Bryan and Jeffrey Collins contributed to this report.

Missouri health officials are investigating dozens of confirmed or probable cases of cyclosporiasis, the intestinal infection that has sickened thousands of people across the country this summer.

As of Sunday, the state Department of Health and Senior Services logged 43 cases of the infection, which causes diarrhea and other digestive symptoms. The department data does not include where in the state cases have been reported.

Missouri has a relatively small number of reported cases compared to Michigan and other states at the center of the outbreak.

Illinois health officials have reported 216 cases of the infection, according to the state’s health department. In Michigan, which has the most reported cases, health officials have logged more than 3,700 cyclospora infections.

Officials expect that number to go up as more people are tested. Because people with diarrhea rarely go to the doctor and even fewer of those people receive the necessary stool sample test, it’s likely more people are infected.

Local health departments are following up with patients to get their food and travel history, which could help identify where the parasite came from.

Cyclosporiasis can cause watery diarrhea, nausea and dehydration. Unlike other illnesses caused by food-borne pathogens, fever and vomiting are relatively rare symptoms. Most people recover from the infection without treatment, but antibiotics can clear the infection.

According to the federal Centers for Disease Control and Prevention, no deaths have been reported due to the current outbreak.

Cyclospora, a parasite that can only be seen through a microscope, is spread through human feces. Past outbreaks have been linked to leafy greens, but officials have not yet found the cause of this year’s outbreak.

People can prevent the illness by thoroughly washing produce, cutting off bruised or damaged bits and refrigerating cut fruits and vegetables. Heat kills the parasite, so cooking vegetables can also cut down on risk.

ROANOKE COUNTY, Va. (WDBJ) – A Bent Mountain teenager will compete at the National High School Rodeo Finals in Lincoln, Neb., later this month after qualifying with the Virginia High School Rodeo Association.

Kellen Hamm, a dual-enrolled homeschooled Roanoke County senior, graduated this May with a 4.2 GPA. She will compete at the national finals July 18–25 in four events: breakaway roping, team roping, barrel racing and pole bending.

Seventh state title in pole bending

Hamm recently claimed her seventh consecutive Virginia state championship in pole bending, riding her horse Tucker. Winning seven straight state titles in the same event on the same horse is considered a rare accomplishment in high school rodeo competition.

College plans

Hamm has been accepted to Murray State University in Kentucky, where she plans to enroll this fall. She will pursue a degree in elementary education and compete on Murray State’s collegiate rodeo team.

To follow Hamm’s progress at the National High School Rodeo Finals, visit the event’s official website online.