(AccuWeather) -- The dome of heat that has baked the southwestern United States through July and obliterated long-standing temperature records will expand its reach over the center of the country and affect millions more with dangerously hot weather.

AccuWeather forecasters say that while the pattern may not promote widespread record high temperatures over the Central states, similar to what has been experienced over the Southwest, many locations could experience the most sustained period of heat and humidity yet this summer.

Cities across the central United States have largely avoided long stretches of intense heat so far this summer.

During the first three weeks of July, temperatures were near or slightly below the historical averages as a whole in places such as Denver, Minneapolis, St. Louis, and Chicago.

"As the record-breaking heat wave continues in the Southwest, by the latter part of the new week, the heat will build eastward into the Midwest as well," AccuWeather Senior Meteorologist Dan Pydynowski said.

High temperatures will climb to levels 5 to 15 degrees Fahrenheit above the historical average as the high pressure system associated with the intense heat grows in size and intensity.

Denver has yet to hit the triple-digit mark yet this year, but the AccuWeather forecast has the city nearing 100 degrees Fahrenheit on Monday.

A triple-digit reading would tie the daily record set in 2003. In 2022, the Mile High City achieved this temperature reading on June 11, which tied the date for the earliest on record. The city's latest 100-degree temperature is Aug. 18.

The heat will continue to expand eastward as the last week of July progresses, bringing lengthy stretches of 90-degree days to Kansas City, Missouri, Minneapolis, St. Louis, and Chicago. For some, this can be the longest stretch of 90-degree weather yet this year.

"Chicago's O'Hare International Airport has not reached 90 since July 14, but 90s are expected to return starting on Wednesday as the heat and humidity build eastward," Pydynowski said.

Highs in the 90s could last through Friday, making for the most sustained period of heat and humidity the city has experienced since July 4-5.

St. Louis may string together a more than week-long stretch of 90-degree temperatures starting on Sunday and lasting into early August. The city's longest 90-degree stint this summer lasted five days from July 10 to 14.

AccuWeather RealFeel® Temperatures can surge into the upper 90s and lower 100s at times within the pattern when factoring in some humidity, sunshine, and drier conditions.

Episodes of severe thunderstorms and flooding are expected to be less frequent compared to recent weeks, providing some glimmer of good news amid the heat.

By the end of the week, a surge of heat will expand even farther eastward and could impact part of the Northeast's Interstate-95 corridor.

"Many residents in the Southwest may be wondering when the extreme heat will break. Normally, the seasonal monsoon provides relief in the region, but it hasn't been anywhere to be found so far this summer," AccuWeather Senior Meteorologist Bill Deger said.

For months, AccuWeather's long-range team has noted that this year's monsoon would be weaker and start later than in years past, and that has certainly been the case this year.

The North American monsoon brings an uptick in cloudiness and rainfall that suppresses the heat and typically runs from June 15 to Sept. 30, according to the National Weather Service's definition.

"Until the monsoon arrives, temperature records will continue to be broken," Deger said.

Phoenix is enduring one of its most intense heat waves ever endured in recorded history and it shows no sign of letting up next week, according to AccuWeather's forecast.

"Even Los Angeles, which has experienced below-average temperatures to begin summer, will begin a run of 90-degree afternoons by the middle of the week," Deger said.

Farther north, areas of the interior Northwest that have faced days of highs in the upper 90s to middle 100s, such as Boise, Idaho, will be some of the lucky few that get a reprieve from the intense heat by the middle of the coming week, forecasters say.