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A violent storm that ripped through northeastern Minnesota early Thursday killed a 13-year-old Boy Scout and a troop volunteer when a tree fell on their tents.

Two other campers were seriously injured.

From northern Minnesota to the Twin Cities, overnight storms downed trees and power lines, leaving thousands of people without electricity and air conditioning in the midst of a dangerous heat wave that will continue through Friday. Relief from the heat is expected after possible severe storms on Saturday.

Campers in the Boundary Waters Canoe Area Wilderness and on Canadian border lakes were rousted from their sleeping bags about 3 a.m. Thursday as wind and rain buffeted tents, tossed canoes and knocked down trees.

The Boy Scout group, a group of nine people camping on the Canadian side of Basswood Lake in Quetico Provincial Park, sent out a distress call around 5:15 a.m. and a floatplane was sent out, said Lt. Nate Skelton of the St. Louis County Sheriff’s Office. Rescue squads from Lake County also responded.

The rescue mission was difficult because many roads and trails were blocked by downed trees in and around the Superior National Forest, said spokeswoman Kristina Reichenbach.

“This is a very difficult time for our Scouting family,” the Boy Scouts of America said in a statement.

Ontario Provincial Police identified the dead as Christian James Sanchez, 13, of Lewisville, Texas, and Rorth Lac, 39, of Carrollton, Texas.

Strobe-like lightning

Torrential rain and “hurricane-force” winds wreaked havoc minutes after strobe-like lightning lit up the night sky, said Joe Krasselt of Minneapolis, who was camped with his wife and four others on Pipestone Lake in the BWCA.

Water flooded into their tent as the wind began to collapse it with them in it. The wind pulled another tent from its stakes, lifting it into the air with Krasselt’s friend still inside. Moments later, a red pine with a trunk circumference larger than Krasselt’s 6-foot arm span fell between that tent and another. Another tree fell while another camper was in a hammock tied to it. The party frantically searched for — and found — another camper who had been sleeping in a hammock.

Krasselt suffered a broken toe from running around barefoot in the dark, but no one else in his group was hurt.

“My heart goes out to the families” of those who died during the storm, he said.

Hard hit

The storms slammed northern Minnesota the hardest, with downed trees taking out power lines and making some roads impassable for a time. Wind gusts measured at the Duluth airport reached 69 miles per hour. A 72-mph gust was measured on Lake Superior, said Dean Melde, a meteorologist with the National Weather Service in Duluth.

Many trees were uprooted, and some fell and became entangled with power lines. At the height of power loss, 46,000 Minnesota Power customers in Duluth and nearby areas were without electricity.

More than 30,000 customers in the region were still without electricity Thursday evening, said Amy Rutledge, Minnesota Power spokeswoman.

“It could be three or four days for power to be restored in some Duluth neighborhoods,” she said.

Thursday’s storm caused the most damage the company’s electrical system has experienced since a 2001 ice storm knocked out power in a broad area, Rutledge said.

High winds also snuffed out power in parts of the Twin Cities, where winds gusted up to 40 mph. About 26,000 Xcel Energy customers lost electricity at the height of the storm, but company officials said all power was likely to be restored by late Thursday.

Meanwhile, stifling heat

For most metro area residents, the bigger issue was a second consecutive day of oppressive temperatures and humidity that combined to make it feel well over 100 degrees.

The heat wave in the Twin Cities will continue Friday, with a heat index that make it feel like 100 to 105 degrees, said Joe Calderone, senior forecaster with the weather service in Chanhassen.

To make matters worse, the metro area also will be under an air pollution health alert from 11 a.m. to 9 p.m. Friday, with intense heat and bright sunlight producing dangerous levels of ozone. People with respiratory or heart conditions, as well as the elderly and young children, should limit strenuous outdoor activities, especially in the afternoon and evening, according to the Minnesota Pollution Control Agency.

High airborne ozone levels can cause shortness of breath, coughing and throat pain and can aggravate preexisting lung and heart ailments.

Relief from the heat will come this weekend on the heels of possible severe thunderstorms predicted for Saturday, Calderone said.

Next week, temperatures will drop to the mid-80s and dew points will fall into the 60s. “It will be far more comfortable compared to what we have now,” Calderone said.

The Associated Press contributed to this report.

marylynn.smith@ startribune.com • 612-673-4788

tim.harlow@startribune.com • 612-673-7768