Severe storms to bookend sweltering heat in Northeast
The heat wave will be the second of the year for several major cities and some areas could be at risk for damaging storms and flash flooding late through the weekend.
As the heat continues to build across the Northeast, rounds of severe weather will renew the flash flooding threat from New York to New England.
As the hottest weather of the summer so far builds across the northeastern United States to end this week, rounds of severe thunderstorms with high winds will be on the prowl, and some locations may have to face a familiar flash flooding problem, AccuWeather meteorologists say.
During a strange summer in the Northeast where Canadian air and wildfire smoke held temperatures back in June and tropical moisture caused downpours and thunderstorms to flourish during much of July, many people are probably looking forward to some days full of non-eventful weather conditions.

However, while it seems that Mother Nature will turn up the atmospheric thermostat, she will not provide much of a break from summertime thunderstorms.
Highest temperatures of the summer so far forecast for millions
In many locations, the late-week heat will make a mark on the summer of 2023 with what may end up being the highest temperatures of the season so far and perhaps for the duration of the summer in some cases.

As temperatures make a run into the upper 90s Fahrenheit in Baltimore and the mid-90s in Washington, D.C., New York City and Philadelphia are among the major metro areas where temperatures will peak at or above the 90-degree mark for three days in a row — the official designation for a heat wave in the Northeast.
This will be the first heat wave of the summer for New York City, and after reaching a high of 92 on Thursday, highs of 93 and 92 are forecast on Friday and Saturday, respectively. Based on AccuWeather's exclusive HeatWave Counter and Severity Index™, which quantifies and measures the heat duration and intensity, this heat wave will be at a moderate level of 4. On July 5, the temperature reached 93 F in the Big Apple, the highest temperature of the year so far there.
The temperature could challenge the daily record high of 97 on Friday in New York City, which was set most recently in 1999.

The historical average for high temperatures in late July in New York City is 85.
Farther south along Interstate 95, Philadelphia already endured a brief moderate heat wave from July 5–8. This heat wave will also last four days, but temperatures will be substantially higher on one or more days, and that will push the HeatWave Counter and Severity Index™ to a 10.
Earlier this summer, temperatures peaked at 93 degrees on July 5. However, during this week's unfolding heat wave, Philadelphia's high of 94 from Thursday will be followed up by temperatures reaching 97 and 94 on Friday and Saturday, respectively.

The historical average high for Philadelphia in late July is 88.
Farther north along I-95, a stretch of hot weather is in store as well in Boston. However, with only one day with high temperatures in the low 90s — Thursday, when a high of 91 occurred — conditions will fall short of an official heat wave in the Massachusetts state capital. Highs in the mid-80s will follow on Friday, which is still a few degrees above the historical average of 82.
AccuWeather RealFeel® Temperatures will run 5–15 degrees higher than the actual temperature at various points of the day. The RealFeel temperature takes into account many different factors such as cloud cover, wind, sun angle and humidity to offer a better idea of how hot it actually feels outside.

Severe storms return this weekend
Any thunderstorm activity Friday in the Northeast is likely to be very spotty in nature. In places where it does manage to rain, it may only do so for a few minutes. However, the period from Friday afternoon to Friday afternoon is likely to be very active in terms of severe weather for the Midwest.
The risk of severe thunderstorms will ramp up this weekend in the Northeast as a front pushes southward.

"As cooler air lunges southward from Canada this weekend, thunderstorms will erupt along the leading edge of the temperature change and will progress from north to south across the Northeast," AccuWeather Senior Meteorologist Brett Anderson said.
People with outdoor plans this weekend should closely monitor the weather situation, as rapidly changing conditions are likely.
Some of the storms are bound to produce high winds, sudden lightning strikes and torrential downpours.

Storms are likely to stretch from parts of the Ohio Valley and central Appalachians to the upper mid-Atlantic and southern New England Saturday and then farther south over the Appalachians and lower portions of the mid-Atlantic Sunday.
The storms are most likely to be severe where they hit during the peak heat of the afternoon and early evening.
Cool air will take over early next week
The storms over the weekend will bring an explosive end to the heat wave, as much cooler and less humid air will move in later this weekend and early next week.

Temperatures will be slashed by 10–15 degrees in many areas, which will mean widespread highs in the 70s over the central Appalachians and northern New England. Elsewhere, temperatures will settle in the low to mid-80s near the mid-Atlantic coast.
It is likely that northwesterly winds will periodically usher some smoke and haze from wildfires burning in western Canada into the region later this weekend to next week.

When the smoke is limited to high levels of the atmosphere, the sun may appear hazy. However, when the smoke is able to mix down to near the ground, poor to unhealthy air quality may return to some locations.
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