CNN  — 

The first heat wave of the season begins Sunday and continues into the workweek for much of the eastern US.

While we’re not yet officially in the summer, Mother Nature is playing by her own rules. Over 30% of the US population will experience temperatures of at least 90 degrees or higher this week.

“The warm, smothering embrace of a high-amplitude ridge will continue into the long term period,” says Kyle Theim, a meteorologist at the National Weather Service office in Atlanta. “Temperatures starting on Monday will run between 10-15 degrees above normal, and border on record maximum temperatures, both for daily highs and lows.”

weather record heat eastern us 052221

More than 70 daily heat records may be broken from Sunday through Wednesday, as a high-pressure system dominates the eastern half of the country. Some cities such as Atlanta, Nashville, Tennessee, Baltimore, and Montgomery, Alabama, are forecast to have multiple days of record heat.

Some places got a head start Saturday as temperatures crept into the low 90s, setting or tying records including Atlantic City, New Jersey, hitting 94 degrees (the old record was 91 set back in 1992.) Georgetown, Delaware, hit 93 degrees, breaking the previous record of 92 from 1996.

There will be a brief break for about two days in some mid-Atlantic and Northeast cities.

“A strong cold front pushes through late Sunday night into early Monday morning, finally giving us a reprieve from the recent summer-like warmth and humidity,” the NWS office in Boston said.

weather 4 day temp map heat wave 052221

However, as quickly as the heat retreats, it comes right back again.

Boston goes from the low 90s Sunday, down to 60s and 70s Monday and Tuesday, then right back up to the 90s again on Wednesday. Washington, DC, Philadelphia, and New York will experience a similar temperature roller coaster.

Boston, New York and Lexington, Kentucky, typically see their first 90-degree day after June 1. However, each of these cities will see those temperatures at least once over the next five days. Washington, DC, is forecast to have multiple days above 90 degrees, including Wednesday, which is forecast to hit 97. Their first average 95 or higher degree day doesn’t usually arrive until June 21.

weather first 90 degree day 052221

The intense heat this early tends to catch people off guard. So make sure you stay hydrated, wear light-colored clothing, wear sunscreen, and never leave people or pets inside a car on a hot day.

CNN meteorologist Gene Norman contributed to this story