Though heat wave began to subside from the eastern side of the U.S. on Sunday, heat advisories are very much in effect in the region as well as across the country.

“Excessive heat warnings and heat advisories are in effect for much of the central U.S. and Ohio Valley, as well as areas from the eastern Carolinas northward into the New York City area,” National Weather Service (NWS) said in a statement.

With rising humidity levels because of this year’s record-breaking heat wave in U.S., NWS warned citizens of the possible heat-related illnesses.

“Heat is the number one weather-related killer in the United States, resulting in hundreds of fatalities each year. In fact, on average, excessive heat claims more lives each year than floods, lightning, tornadoes and hurricanes combined,” it said.

According to National Oceanic and Atmospheric Administration's (NOAA) NWS, over 1,250 people died from excessive heat conditions as disastrous heat wave swept across the country in 1980.

More than 700 fatalities were reported because of heat in the Chicago area in 1995, while in Europe, August of 2003 saw a record death toll of about 50,000 people because of heat wave, it added.

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This map shows forecast temperatures for the US. PHOTO: NOAA/NWS