(NEW YORK) -- A life-threatening heat wave has enveloped the East Coast, hitting cities with the worst of the high temperatures on Tuesday before relief moves in later in the week.
This is the first major heat wave of the season, with extreme heat warnings and heat advisories in effect for over 150 million Americans from Texas to Maine, including the entire Interstate 95 corridor.
Extreme heat warnings are in effect across the Northeast, including Boston, New York City, Philadelphia, Baltimore and Washington, D.C. Actual temperatures are approaching 100 degrees, while the heat index -- what the temperature feels like with humidity -- is soaring above 100 degrees.
Philadelphia, Baltimore and Raleigh, North Carolina, all broke daily heat records on Monday with temperatures of 99 degrees, 104 degrees and 100 degrees, respectively. In New York City, the heat index on Monday reached 106 degrees -- the highest in the area in four years.
Tuesday is the hottest day of the heat wave for the Northeast.
Boston hit 101 degrees on Tuesday -- the city’s hottest June temperature on record. Philadelphia reached 100 degrees for the first time in 13 years, while New York City measured at 99 degrees -- a new daily record.
With the heat index, it feels like 106 degrees in Boston, 101 in New York City, 105 in Philadelphia, 110 in Washington, D.C., 108 in Charlotte, North Carolina, and 107 in Charleston, South Carolina.
Amtrak said some trains in the Northeast may be delayed due to heat-related speed restrictions. Amtrak issues these restrictions when temperatures are higher than 95 degrees and the tracks reach 128 degrees.
The extreme heat will even reach upstate New York and New England, where the heat index is forecast to hit 102 degrees.
This kind of rare, long-duration heat with little overnight recovery can be life-threatening, especially for people without adequate cooling or hydration available.
Con Edison is urging everyone in New York City to conserve energy.
"Customers' need to run their air conditioners to stay comfortable place stress on electric delivery equipment," Con Edison explained. "The company asks customers to refrain from using intensive appliances such as washers, dryers, and microwaves during peak hours."
Relief from the oppressive heat will arrive on Thursday. Temperatures will drop to 69 degrees in Boston, 78 in New York City, 91 in Philadelphia and 93 in D.C.
Click here for what you need to know to stay safe in the heat.