The Midwest braces for severe storms capable of ‘hurricane-force’ winds.

U.S.|The Midwest braces for severe storms capable of ‘hurricane-force’ winds.

• July 28, 2021, 6:59 p.m. ET

Cities across the Midwest were bracing for severe thunderstorms on Wednesday night that had the potential to produce “hurricane-force” winds.

The National Weather Service’s Storm Prediction Center warned of moderate severe weather that could affect more than 5.9 million people in Grand Rapids, Mich., and the Wisconsin cities of Milwaukee, Green Bay, Kenosha, Racine and nearby areas.

The center said in an update that the storms had the potential to produce “widespread and potentially significant wind damage.” The Weather Service office in Milwaukee said the storms had the potential to produce winds greater than 70 m.p.h. and tornadoes.

“All severe weather hazards are possible, but a swath of damaging winds, possibly hurricane force, remains the primary threat,” the Milwaukee office said on Twitter.

Ben Miller, a meteorologist with the Weather Service, said the line of storms had the potential to become what is known collectively as a derecho (pronounced deh-REY-cho).

Derechos are widespread wind storms that have the potential to produce damage similar to what tornadoes can inflict. For a storm system to be considered a derecho, the swath of wind damage must extend more than 240 miles with wind gusts of at least 58 m.p.h.

Last August, a derecho tore through portions of the Midwest, leaving more than 250,000 people without power in Illinois and Iowa. At least two people were killed as a result of the severe weather, and millions of acres of crops were damaged.

The National Weather Service was urging residents in the forecast area of moderate severe weather to have ways of staying informed throughout the night. “You need to have a way to get the warnings because you might sleep through something that you might want to protect yourself from,” Mr. Miller said.

The Weather Service office in Green Bay warned of possible power outages and said the storms would most likely be fast-moving, leaving “little time to seek safe shelter.”

Several cities were just outside the projected band of moderate severe weather, including Chicago, Madison, Wis., South Bend, Ind., and Lansing, Mich. The Weather Service office in Chicago said the severe weather threat was expected to arrive around 1 a.m. and 4 a.m.

“A line of storms capable of downing trees and powerlines exists, but uncertainty in where the core of strongest winds tracks remains,” the office said in a tweet.