Heat to finally build into mid-Atlantic, Northeast this week

Following a lack of heat so far this month in the mid-Atlantic and Northeast, many cities will be thrust into 90-degree Fahrenheit temperatures and the year's first heat wave this week.

"An area of high pressure will build over the eastern part of the nation during the second half of the week," AccuWeather Meteorologist Ryan Adamson said.

The jet stream will bulge northward over the northern tier of the nation this week, allowing the heat to spread eastward from the Central states to the Eastern Seaboard.

"On Wednesday, most temperatures throughout the eastern Great Lakes, mid-Atlantic and southern New England will be in the middle to upper 80s Fahrenheit," Adamson added. "The exceptions will be 70s F and lower 80s F at the beaches and lower 90s F in places like Philadelphia, Baltimore and Washington, D.C."

Humidity levels, while noticeable, will still not be too oppressive on Wednesday, so the outdoor air should feel around what the actual air temperature suggests.

However, more humid air is forecast to accompany the heat during the final two days of the week as moisture is drawn northward from the southern United States.

High temperatures during late week will rise even higher, into the upper 80s F across interior regions and middle 90s F along the Interstate-95 corridor.

A weak disturbance sweeping across New England on Wednesday and Thursday will put a cap on how far north the 90-degree heat can surge.

From New York City and points north and east, high temperatures in the 80s F will be more common on a daily basis this week.

The combination of sunshine and humidity can drive AccuWeather RealFeel® Temperatures toward the century mark late this week from Philadelphia to Washington, D.C., and into the lower 90s F from New York City into southern New England.

Areas across the central Appalachians can also have RealFeel Temperatures in the lower to middle 90s F.

This will be the first official heat wave, defined as three or more consecutive days with highs at or above 90 degrees, of the year in many cities.

Lancaster, Allentown, York, Harrisburg and Philadelphia, Pennsylvania; Trenton, New Jersey; Hagerstown, Maryland; and Dover, Delaware; are among some cities that have yet to experience a heat wave this year, but are expected to this week.

"With the hot, stagnant air remaining parked over the area for several days, air quality will begin to deteriorate by the end of the week and into the weekend," Adamson warned.

Children, the elderly and those with asthma or other respiratory ailments should limit time outdoors and take frequent breaks from the heat, particularly during the late afternoon and early evening when temperatures are highest.

In addition, anyone that is spending prolonged time outdoors should be sure to drink plenty of fluids and stay hydrated to minimize the risk of heat-related illnesses such as heat exhaustion and heatstroke.

Because there has been a lack of heat across the region so far this year, many people's bodies have not yet acclimated to the higher temperatures and can succumb to these illnesses more quickly than during the latter half of the summer.

"There will also not be too much cooling at night, especially in urban areas, resulting in higher electric bills as cooling demand increases around the clock," said Adamson.

Air conditioning units will get a workout this week as lows only dip down into the 70s F in the cities and 60s F in outlying areas.

Although the heat and humidity will peel back slightly this weekend, it will still feel like summer across the mid-Atlantic with no return to a cooler weather pattern in sight through at least the Fourth of July holiday.

The exception will be across New England, where a stronger push of cooler air will put an end to the summerlike heat later this weekend into early next week.

Download the free AccuWeather app to see how high temperatures will get in your community this week. Keep checking back for updates on AccuWeather.com and stay tuned to the AccuWeather Network on DirecTV, Frontier and Verizon Fios.