As heat reaches its peak in the East through Thursday, the clock is ticking on the arrival of cooler, less humid air for the region.
The pattern of cool air rolling out of Canada during recent weeks will soon resume.
Just when you thought summer was here to stay, a cool front will push into the Appalachians and New England during Friday, then to the mid-Atlantic coast by Saturday.
During the transition, thunderstorms are likely to erupt.
While far from a blast of cool air, the first push from Canada will take the edge off the heat and replace dangerous conditions with levels that are much less troublesome. High temperatures in the 90s to near 100 will be replaced by high temperatures in the 80s.
However, the atmosphere will not stop there. More air will flow southeastward from central Canada, and by the middle of next week, temperatures could be running 10 to 15 degrees below normal. This would put highs in the 60s to lower 70s.
Some cooler air will also spill into part of the South next week.
The jet stream, which is a belt of strong steering winds high in the atmosphere, is forecast to take another big southward dip into the Great Lakes and Eastern states next week.
If it rains in some areas during part of the pattern, which is possible in part of the Appalachians and Atlantic Seaboard, daytime highs could be even more off the mark.
The sunny versus rainy weather during the first part of next week may be contingent on the movement of a tropical system, which has yet to be born in the Gulf of Mexico or western Caribbean.
The feature could draw rain and humid conditions up the coast for a time, followed by windy, chilly air from the northwest.
At any rate, after the blast of heat moves away late this week, there is no sign of 95- to 100-degree air returning any time soon for the region.
The first and middle phases of the pattern are not likely to bring much rain to needy areas of the Ohio and middle Mississippi valleys. It is possible that moisture will begin to feed into these areas late in the month from the northern Rockies and central Plains.
Until the first front arrives, tens of millions of people will continue to swelter in a dangerous blast of high heat and humidity that few are accustomed to.
Tropical Depression Two has formed in the Atlantic and could become the next tropical storm of the season by midweek.
Severe storms will rumble through parts of the Midwest, including Chicago, early Tuesday night.
Warm and humid air in place over much of the Midwest and Northeast at midweek will contribute to the risk of drenching, gusty and locally severe thunderstorms on Wednesday.
After temperatures briefly climb to typical midsummer levels, another cooldown will roll into the Midwest and expand to the East for the last part of July.
With the recent heat fading away, more relief will greet the Northwest by midweek in the form of rain.
Simla, CO (1996)
4.5" diameter hail.
Mid-Atlantic Ocean (1788)
(22nd-24th) George Washington Hurricane; After causing ship disasters off SW Bermuda, the storm moved NW over Tidewater, NC and VA to pass right over George Washington's Mt. Vernon plantation. On July 24th, George Washington wrote in his diary: "About noon the wind suddenly shifted from NE to SW and blew the remaining part of the day violently from that quarter. The tide this time rose near higher than it was ever known to do, driving boats, etc. into fields, where no tide had ever been heard of before, and most, it is apprehended, having done infinite damage on their wharves at Alexandria, Norfolk, Baltimore, etc. At home all day."
Canton, IL (1975)
A tornado ripped through a 3-block section of downtown, killing 2 people, injuring 75 and creating $5 million damage. A 15-foot wooden plank was driven through an auto engine block, splitting the front of the car in two. The woman driving was not injured. National Guardsmen were called in to prevent looting.