Central, Eastern United States Brace For Massive Heat Wave

A heat wave sweeping across the United States is expected to bring heat indexes of over 100 degrees to much of the Central and Eastern parts of the country this weekend.

Hazardous weather advisories have been issued for New York City, Philadelphia, Washington, D.C., and other major cities. The National Weather Service said that 124 million people are under some sort of heat watch, warning or advisory.

The service called heat exhaustion a "silent killer," as many people don't realize they are suffering from it until it is too late. People under these advisories are urged to drink lots of water, stay inside when possible and schedule outdoor activities for early morning or evening hours.

In New York City, officials asked citizens to check on their elderly neighbors, who may be more prone to heat exhaustion as the temperature approaches 100 degrees.

"Extreme heat affects people of all ages, but some New Yorkers are more vulnerable than others, especially the elderly and people with chronic medical conditions," New York City Commissioner Joseph Esposito said in a statement. “Stay safe by staying cool — use air conditioning, drink lots of water and check in on friends and family."

Along with the heat, an Air Quality Advisory was put in place in the city for heavy smog levels. The state warns people sensitive to elevated ground-level smog should avoid prolonged periods outdoors and limit exercise.

Temperatures in Boston will approach 100 degrees.

Washington, D.C., could top the century mark for the first time in four years. The city's most famous resident shared a warning about the weekend weather on Twitter:

In the president's hometown of Chicago, the heat index could reach 115 degrees.

There is also a “limited severe thunderstorm risk” on Saturday and Sunday in the city. Thunderstorms on Saturday could increase in coverage through Saturday night, according to the National Weather Service.