As cool air begins to cut into surging heat and humidity from the Great Lakes to the Northeast, locally severe thunderstorms will affect some communities and may disrupt travel.
Many of the storms will bring brief gusty winds, downpours and a few lightning strikes. However, a small number of the storms can be locally severe with damaging wind gusts, hail, flash flooding and frequent lightning strikes.
During Wednesday, the storms fired around the I-90 corridor of the United States from Chicago to Albany, N.Y., northern New England and from Toronto to Montreal and Quebec City, Canada.
On Thursday, storms will reach from Pennsylvania to Maine and northern New Brunswick, Canada. after affecting part of the I-81 corridor in Pennsylvania and New York state during the afternoon, the greatest chance of regional travel disruptions and severe weather along the I-95 corridor will be during the evening.
Cities that can be impacted by a heavy, gusty thunderstorm to perhaps more severe weather include Washington, D.C., Baltimore, Philadelphia, New York City and Boston.
A few disruptions from locally strong storms can also occur Thursday evening over the Tennessee Valley to the southern Appalachians.
In addition to the potential for blinding downpours and flash flooding, sporadic power outages are possible.
Much cooler will sweep eastward and southward in the wake of the storms by the end of the week.
For parts of the region, a reasonable amount of rain would not be a terrible thing. Despite a wet June and July in many areas, a few locations have become dry in recent weeks.
Washington, D.C., and Scranton and State College, Pa., have only received about one-third of their normal rainfall from Aug. 1 to Sept. 11. Baltimore, Md., has received less than one-quarter of its normal rainfall in the past six weeks.
The combination of the rainfall from the storms and the cool air that follows may give allergy suffers a little break, by washing and sweeping away dust, pollen and poor air quality in general.
Cool and unsettled weather will continue across the Northeast through late week.
Relief is on the way for portions of the Plains that are in the grips of the ongoing drought.
A tropical wave west of the Cape Verde Islands looks like it could be the next named tropical storm in the Atlantic Basin.
It was a rather active past few days with tornadoes, flash flooding, and damaging winds targeting many communities from Tennessee to Massachusetts and in Colorado.
A pair of tropical threats will target areas from China and Taiwan to Guam this week.
Following the thunderstorms of early in the week, the Nation's Capital will see cooler and less humid air midweek.
Burlington, NJ (1925)
Large amount of hail fell and remained on the ground for 3 days.
Colorado Springs, Colorado (1978)
A freak thunderstorm dropped damaging hail to a depth of 2 feet. Much of it had to be plowed from the freeway.
July 29th is historically a rainy day in Waynesburg, PA. It all began in 1878 when a farmer casually told drug store clerk William Allison that it always seemed to rain on July 29th in this southwestern PA town. The clerk made a note of it and started keeping a yearly tabulation. July 29th, 2001 was the 104th rainfall in the past 124 years on this date.