People living in areas along U.S. eastern seaboard awoke to unusually hot weather Tuesday morning, with temperature in major cities in Northeast expected to reach the 100 degree Fahrenheit (over 37 degrees Celsius) mark.

According to estimates, Washington D.C. is to see the thermometer reach 102 degrees Fahrenheit (nearly 39 degrees Celsius), and Philadelphia will be boiled by the same high temperature.

Elsewhere in the Northeast "megalopolis region," which also include Boston, New York and Baltimore, the highest temperature is expected to be around 100 degrees Fahrenheit. National Weather Service has issued a heat alert for the area, and an additional "excessive heat warning" for Wednesday.

The heat wave is believed to be the most intense since 2001, as National Weather Service officials have advised people to stay indoors to avoid the prolonged heat and humidity, which have created a "dangerous situation."

A hot air mass has descended into the Eastern seaboard Sunday, bringing with it a hot and humid Fourth of July. The heat wave tightened its grip since.