(NEW YORK) -- Millions of Americans will face dangerous heat this week, as a new heat wave is expected to bring near triple-digit temperatures to the South.
The Southeast and the Plains will experience temperatures between 10 and 20 degrees above average with humid conditions, according to the National Weather Service.
Heat wave continues in 27 states across the country
While the Northeast felt a reprieve from the heat this weekend, heat alerts were in effect on Sunday in the Upper Midwest, as temperatures in the Plains hit 100 degrees and higher.
Temperatures in Fargo, North Dakota, hit 102 degrees on Sunday, while North Platte, Nebraska, reached 100 degrees. Low humidity has kept heat indexes low in the Midwest, a far cry from last week's "heat dome," which caused the heat index in the region to reach 115 degrees.
Midwestern cities could hit their daily record highs by Monday afternoon.
The Central U.S. region will see highs in the 90s as the heat travels east but won't see high heat index values because it won't be very humid.
Millions of people in the Midwest will eventually see a break this week as the heat moves into the South, where cities such as Atlanta, Memphis and New Orleans will see temperatures hit close to 100 degrees.
Summer officially begins on Tuesday, and for the rest of the month, swaths of Central and southern parts of the U.S. are expected to see above-average temperatures.
More than 1,300 people die every year in the U.S because of extreme heat, according to the Environmental Protection Agency.
The excessive heat, coupled with strong winds and arid conditions, has sparked fears of wildfires in the West. The National Weather Service issued "red flag" warnings in Flagstaff, Arizona, and Price, Utah.
According to the NWS, "red flag" warnings occur when "warm temperatures, very low humidities and stronger winds are expected to combine to produce an increased risk of fire danger."
While the potential for wildfires will dwindle in the next few days, the conditions will make it harder for firefighters to battle existing wildfires in the Southwest.
Due to the monsoon season, rain is expected over the next day in parts of the country that have experienced widespread drought and wildfires, such as Texas, New Mexico and Colorado, making the areas more susceptible to flash floods.
Historic flooding emergency in the Northern Rockies, high temperatures
Last week, Yellowstone National Park closed after historic flooding destroyed homes, washed out roads and left many people stranded.
ABC News' Dan Peck contributed to this report.