As cooler air drives into the sea of heat and humidity in the East, locally powerful thunderstorms will continue to develop into this evening.
Relief is coming for those with heat-sensitive health problems, but big thunderstorms are marking the transition.
There is a risk of strong to perhaps damaging thunderstorms this afternoon and evening along the I-95 corridor from Richmond to Washington, D.C., Baltimore, Wilmington, Philadelphia, Trenton, New York City, Hartford, Providence and Boston.
While the storms will not be severe in every neighborhood, they can bring a brief period of damaging wind gusts and blinding downpours to many locations.
A few communities can be hit with downed trees and power outages, frequent lightning strikes, urban flooding and hail.
Much cooler and drier air will work in aloft, while the air remains hot and humid at the surface into this evening.
This setup produces an unstable atmosphere that can be made acute by the approach of the cooler air at the surface.
Folks spending time outdoors into this evening should keep an eye out for rapidly changing weather conditions and seek shelter in a building away from windows as storms approach.
In addition to the heat, the approach of the storms could lead to delays at area airports and poor visibility on the highways, due to blinding downpours.
Tropical Storm Matthew has formed in the Caribbean could take a turn toward the United States as a hurricane next week.
It will feel like an extended winter for those living from the northern Plains to the eastern U.S., as cold and snowy conditions last longer than normal.
The final day of September will bring a rare lunar event that hasn’t occurred since March of 2014, a Black Moon.
Rain will spread over much of the northeastern U.S. into the weekend, but persistent downpours will raise the flood risk in part of the mid-Atlantic.
A new typhoon is brewing in the western Pacific Ocean and could pose a risk to Japan, Taiwan and eastern China next week.
Thundery showers set to start this weekend will depart before the season's first National Football League game in London kicks off on Sunday.
Terre Bone Parish, LA (1915)
Hurricane hit with 140-mph winds. The storm wrecked 90 percent of the buildings in town. Central pressure of 951.9 mb; 275 killed, $13 million damage.
St. Louis, MO (1927)
Tornado 300 feet across with a 4-mile path crossed river. Twister killed 72, caused $22 million damage. Total of 81 dead from outbreak and $25 million damage.
Colorado Springs (1959)
A storm produced 28 inches of snow.