Over 100 million people across the US are being impacted by a sweeping heat wave that is expected to break records in many parts of the country as it moves east.

The National Weather Service (NWS) said the heat wave would continue through the week as it expands "from the Plains into the Midwest and Southeast."

"Much above normal record tying and record breaking high and low temperatures are forecast. The warm lows will provide little relief from the heat overnight," the NWS said on Sunday.

It said in a separate weather alert that "dangerous heat" is expected to extend from the Mississippi Valley to the Southeast through the middle of the week, and "critical fire weather conditions" would be present in the southwest and central Rockies through the Monday night.

High temperatures are expected to hit the 90s and 100s Fahrenheit "with heat indices likely to be in the upper 90s and 100s."

Excessive heat warnings have been issued for at least 11 states spanning the Midwest, South and eastern sea board while heat advisories have been issued for about a dozen other states.

Multiple reports said the number of people that are being affected surpasses 100 million./agencies