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.

• Sen. Amy Klobuchar is urging the CDC and FDA to restore funding for food safety programs amid a cyclosporiasis outbreak.
• Cyclosporiasis is a gastrointestinal illness caused by a parasite found in contaminated food, often fresh produce.
• Health officials recommend thoroughly washing fresh produce and cooking it to 158 degrees to kill the parasite.

After an outbreak of cyclosporiasis, a gastrointestinal disease, U.S. Sen. Amy Klobuchar is speaking up.

The Minnesota senator is urging the Centers for Disease Control and Prevention and the U.S. Food and Drug Administration to reinstate funding and staffing for federal and state food safety programs to fight the current cyclosporiasis outbreak.

Cyclosporiasis is an illness caused by eating contaminated food or drinking contaminated water and can lead to severe diarrhea, dehydration, fatigue and other health issues. So far across the country, Klobuchar states, nearly 2,800 cases and 87 hospitalizations linked to this outbreak have been confirmed. 

“I write to urge the Centers for Disease Control (CDC) and Food and Drug Administration (FDA) to restore funding and staffing cuts made by the administration to federal and state food safety programs,” wrote Klobuchar. “As a currently uncontrolled large foodborne outbreak across the country continues, cuts to these programs are impacting our nation’s ability to prevent, detect, and contain foodborne illnesses and protect public health.”

Klobuchar said last year the administration made reporting of foodborne illnesses caused by the parasite cyclospora optional when it cut the CDC FoodNet program’s tracking of 10 pathogens, refering to the administration’s layoffs of federal public health employees.

“More recently,” the senator wrote, “the administration terminated Congressionally-appropriated Public Health Infrastructure Grants and Preventive Services Block Grants, which pay for state health department staff, laboratory capacity, diagnostics, tracking, and surveillance.”

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What is cyclosporiasis?

The outbreak of cyclospora is putting health officials on alert as cases of the foodborne illness continue to be investigated across the United States. The illness is caused by the microscopic parasite, which can contaminate fresh produce and cause days, or even weeks, of severe gastrointestinal illness.

Unlike many foodborne illnesses, cyclospora is most often linked to fresh fruits and vegetables that are eaten raw, including leafy greens, herbs and berries. Investigators are working to determine the exact source of the current outbreak while tracing where contaminated food may have been distributed.