Three people died on Friday after their boat capsized in a severe storm on Geneva Lake, a popular tourist destination in southeastern Wisconsin, the Walworth County Sheriff’s Office said.

Seven other people were pulled from the water, Tom Hausner, the Walworth County undersheriff, said at a news conference. Their conditions were not immediately available.

The deaths remain under investigation, Undersheriff Hausner said.

The authorities did not immediately release the identities or ages of the people who died. They also did not say what caused the boat to capsize or if the weather was the sole factor. Undersheriff Hausner said the storm hit around 12:10 p.m., and that’s when 911 calls began to come in alerting the authorities to the boat accident.

Geneva Lake is an elongated lake in southern Wisconsin, about 43 miles southwest of Milwaukee. The city of Lake Geneva, a resort town and popular weekend destination, sits at its eastern end.

Forecasters had warned of the potential for severe thunderstorms across much of the eastern half of the United States on Friday. The storms were moving along the northwestern edge of the high pressure system, often called a heat dome, that has been responsible for the brutally hot temperatures across much of the country this week.

These types of storms can cause hail and even tornadoes, but it was the risk of damaging wind gusts that forecasters were most concerned about as the storms moved east on Friday.

A squall line of thunderstorms moved across Northern Illinois and southern Wisconsin on Friday morning into the early afternoon, with reports of wind gusts reaching 50 and 60 miles per hour, along with snapped trees and downed utility poles. Nearly 514,000 homes and businesses across Michigan, Illinois and Wisconsin were without power Friday night, according to PowerOutage.com, a website that tracks utilities.

The storms swept across Geneva Lake, moving from the southwest to northeast, in the early afternoon and had moved out of the area by 12:40 p.m., according to John Gagan, a meteorologist at the Weather Service office in Dousman, Wis.

“We had multiple local home weather stations west of the lake report wind gusts around 65 miles per hour,” Mr. Gagan said.

The threat of potentially dangerous storms continued Friday night, with clusters of storms spread across a broad area, including over southern Michigan and eastern Pennsylvania.