More than 100 million in Northeast, Midwest bracing for late-July heat wave
A surge of heat will bring the hottest weather of the year to the Northeast late this week.
Heat that has been building all summer long over the Southwest is about to spread into the Midwest and Northeast for several days from the middle to the latter part of this week, AccuWeather meteorologists say. For parts of the East, temperatures will climb to their highest levels of the year so far.
The heat will pale in comparison to the extreme levels experienced in the Southwest in recent weeks. Late July is about the hottest part of the summer based on the historical average for much of the United States. However, temperatures will top the average levels by 6–12 degrees Fahrenheit and could challenge some daily record highs in the Midwest and Northeast.
High temperatures in the low to mid-90s are in store with a few spots potentially closing in on the 100-degree mark.
"This week, the extent of the heat across the United States will be the most widespread of the summer yet," AccuWeather Chief On-Air Meteorologist Bernie Rayno said.
At least 45 states and more than 100 million Americans will experience high temperatures of 90 degrees or higher at some point this week.
Temperatures to surge Thursday and Friday in Northeast
"For people in much of the Northeast, later this week will bring the hottest weather of the summer so far," Rayno said.
New York City will reach or exceed 93 F on Friday — its highest temperature of the year so far — and may hit 92 on Thursday and Saturday, which would make it the first official heat wave of the year in the Big Apple. This three-day heat wave is forecast to have an AccuWeather HeatWave Severity Index™ of 5, which makes it a moderate heat wave.
As a way to help people understand the magnitude of heat, the exclusive AccuWeather HeatWave Counter and Severity Index™ quantifies heat waves by duration and intensity. A heat wave in New York City is considered to be three days in a row with high temperatures of 90 or greater.
AccuWeather's exclusive HeatWave Counter and Severity Index™, quantifies and measures the duration and intensity of heat.
Temperatures will reach or exceed 90 in Philadelphia for four days in a row from Wednesday to Saturday.
Like New York City, three or more days with highs of 90 or greater is considered to be a heat wave in Philadelphia. An AccuWeather HeatWave Severity Index™ of 11 is forecast for the city where the highest recorded temperature so far this summer -- 95 degrees -- is projected to be topped later this week.
AccuWeather's exclusive HeatWave Counter and Severity Index™, quantifies and measures the duration and intensity of heat.
Boston will likely match its season high of 91 on Friday. Since high temperatures are likely to peak in the 80s Wednesday and Saturday, an official heat wave is not likely, but RealFeel™ Temperatures are likely to reach between 95 and 100 in the city.
Temperatures are projected to surge to near 100 in Washington, D.C. and Baltimore. The nation's capital has not exceeded 94 degrees so far in 2023. In Baltimore, the highest the mercury has gotten is 96. Factoring in actual temperatures, humidity, breezes and other conditions, the AccuWeather RealFeel® Sun Temperature may approach 110 for several hours in the afternoon.
On Thursday, temperatures will flirt with record highs for the date in cities such as Washington, D.C., Hagerstown, Maryland, and Charlottesville, Virginia.
Heat to broil Midwest this week
In parts of the Midwest, the heat may be even more extreme than in the Northeast, as it will be closer to the source of hot air in the Southwest.
A massive dome of high pressure has been the driving force of the heat in the Southwest this summer and that system will expand eastward this week.
In St. Louis, high temperatures in the low to mid 100s are likely Thursday and Friday. The highest that temperatures have reached so far this year there is 97 F.
Elsewhere, the highest temperatures so far this summer in Detroit, Cleveland and Pittsburgh have only been around the 90-degree mark prior to this week.
This week's heat should approach those levels by Wednesday and may exceed the high marks Thursday and Friday in many cases.
Chicago will experience its first official heat wave of the summer with four days of high temperatures of 90 or greater from Tuesday to Friday. The season-high temperature mark of 93 may be topped Thursday or Friday.
An AccuWeather HeatWave Severity Index™ of 6, which is moderate, is forecast for Chicago
AccuWeather's exclusive HeatWave Counter and Severity Index™, quantifies and measures the duration and intensity of heat.
Preceding, accompanying and following the heat, thunderstorms will be on the prowl. With a few exceptions, most storms will tend to occur on either end of the heat wave rather than smack in the middle.
AccuWeather meteorologists urge people to seek an air-conditioned environment when possible. Limiting vigorous physical activity during the peak of the heat during the midday and afternoon is recommended, as well as increasing the intake of non-alcoholic fluids to reduce the risk of heat exhaustion and heat stroke.
Canadian air to provide some relief
Starting this weekend, a southward shift in the jet stream will begin to allow cooler air to flow out of Canada.
Temperatures will trend downward around the Great Lakes, New England and the central Appalachians Saturday.
By Sunday, the cooling trend will reach the Ohio Valley and much of the mid-Atlantic region. On Monday, much of the Midwest and Northeast will be noticeably cooler and less humid.
High temperatures will throttle back to the 70s to near 80 from the Great Lakes to New England and the low to mid-80s in the Ohio Valley and mid-Atlantic by early next week.
Accompanying and following the heat will be bouts of poor air quality thanks to smoke from wildfires in western Canada.
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