Violent thunderstorms are already threatening communities across the Midwest today.
A derecho, a thunderstorm complex that produces a continuous line of wind damage, is barreling along the border of Minnesota and Iowa and tracking toward southern Wisconsin.
This derecho and other severe thunderstorms that erupt will continue to threaten the corridor from southern Minnesota and Iowa to the Lower Peninsula of Michigan, northwestern Pennsylvania and southwestern New York through tonight.
While the majority of the strongest thunderstorms will bypass the areas hit in northern Wisconsin on Friday evening, southern Michigan from Grand Rapids to Detroit may face another round of damaging wind gusts late today. Restoration of power can further be delayed or new issues can develop.
A separate area of severe weather is expected to erupt over eastern Colorado during the late afternoon and evening hours of today.
"When an unusually strong cold front moves into an unusually hot and humid air mass, severe weather can be expected," according to AccuWeather Senior Meteorologist Adam Douty, "and that will be the case through Monday."
"The strongest thunderstorms will produce flooding downpours and damaging wind gusts," he added.
On Sunday, the thunderstorms will slice into the sweltering heat over more of the Northeast, Lower Midwest states and back to the central Plains.
"While any thunderstorm can unleash strong wind gusts within that corridor, the area at greatest risk stretches from Ohio to central and southern Illinois," according to AccuWeather Senior Meteorologist Brett Anderson.
This includes the cities of Columbus, Cincinnati and Indianapolis.
Another more concentrated area of severe thunderstorms may develop over Missouri and eastern Kansas.
Drenching and gusty thunderstorms will then focus on areas from the Ohio and Tennessee valleys to the Northeast on Monday. Once again, flash flooding and damaging winds will be concerns.
The greatest risk for severe weather is anticipated from Boston to New York City; Philadelphia and Harrisburg, Pennsylvania; Baltimore and Washington, D.C., during the afternoon and evening hours.
Even in the absence of severe weather, residents in the path of the thunderstorms through Monday will face disruptions to outdoor plans, travel delays and lightning dangers.
"In this type of situation, these thunderstorms will produce a significant amount of lightning," Anderson said. "With people picnicking and doing other activities outdoors, they have to remember that trees and pavilions are not safe places to be during a thunderstorm."
The first clap of thunder is nature's warning that you can be struck by lightning and to seek shelter immediately.
A dramatic and much-welcome reduction in the sweltering heat and humidity will follow the slow-advancing line of downpours and thunderstorms. Temperatures first will be slashed, followed by the high humidity the next day.
The comfortable air will fully sweep over the Great Lakes and northern Plains by Monday before pressing over the Ohio and Tennessee valleys and Northeast Tuesday into Wednesday.
Less humid air may also make a rare July appearance southward to the Interstate-20 corridor at midweek.
EDITOR’S NOTE: Kristina Pydynowski is an AccuWeather senior meteorologist.