Thunderstorms packing torrential downpours and gusty winds will focus over the lower Great Lakes region and part of the Ohio Valley into Friday night.
"A return of warm and humid air combined with series of storm systems moving through will help to fuel thunderstorms from Illinois to upstate New York into the end of the week," according to AccuWeather Meteorologist Max Vido.
"The main threats from the storms will be localized damaging wind gusts and especially flash flooding due to their repeating nature in some communities," Vido said.
Motorists venturing along Interstate 90 from near Chicago to Cleveland, Erie, Pennsylvania, and Buffalo and Syracuse, New York, should be prepared for poor visibility and excess water on the road at times.
Those on the road should reduce their speed during downpours for safety reasons. Excess rainfall can cause vehicles moving at highway speeds to hydroplane. Never attempt to drive through a flooded roadway.
Areas north of I-90 from Detroit and Toronto are also at risk for the dangerous and disruptive storms.
Sporadic power outages and minor property damage are possible.
"A few of the strongest storms may produce large hail as well," Vido said.
Occasionally, severe thunderstorms can produce a tornado.
On Friday, while the threat of severe weather may leave the Milwaukee and Chicago areas, the risk of damaging storms may dip southward to Indianapolis and Cincinnati, Dayton and Columbus, Ohio.
Storms will continue to threaten a large portion of the I-90 corridor on Friday.
"In many cases, the storms on Friday could pack more of a punch when compared to Thursday's storms as far as the risk of damaging winds are concerned," Vido said.
Drenching and locally gusty storms will continue over part of the same area and expand to new territory on Saturday.
On Saturday, areas from upstate New York and northern New England to western Pennsylvania, eastern Ohio, West Virginia and Kentucky could face some nasty weather.
Those spending time outdoors, especially at low-lying areas at campsites, should be especially wary of the risk for flash flooding and lightning strikes.
While isolated thunderstorm activity can reach east of the central Appalachians, severe weather is not likely along the I-95 corridor and the Atlantic beaches through the daylight hours on Saturday.