At least 16 US cities set or tied records for their highest temperature for the date, with Macon, Georgia, hitting 103 degrees Fahrenheit on Wednesday, the National Weather Service reported.
That was 3 degrees higher than the previous June 15 mark in Macon, set in 2010.
Chicago’s O’Hare airport reported a record temperature of 96, which is 15 degrees above normal and well above the 77 degrees it was last year on that date. The prior mark was 95, most recently reached in 1994, according to the weather service.
Records were set in states from Michigan – where the Tri-Cities saw 94 degrees – to Florida, where it was 95 in Tampa, equaling a mark set in 2001.
More than 120 million people were under heat warnings and advisories Wednesday, according to the weather service.
In a midday forecast the agency said: “Life threatening excessive heat will develop across portions of the Midwest” and Georgia will experience “dangerous heat.” There are also warnings or watches in the Southwest, and parts of Colorado, Nebraska, Nevada and Oklahoma.
A total of 32 places across the central and southern US may get close to or exceed high-temperature records, according to the weather service’s Weather Prediction Center. Multiple cities, including St. Louis, Nashville and Charlotte, North Carolina, have already broken daily records this week.
The dangerous temperatures come as many homes remain without power after storms across the Midwest on Monday. That includes about 180,000 customers without power in Ohio on Wednesday, according to Poweroutage.us.
The majority of Ohio has been under an excessive heat warning and about a dozen cities are among those that could set temperature records, according to the weather service. A spokesperson for electric company AEP Ohio told CNN that some customers should prepare for outages to last until Thursday.
Columbus Mayor Andrew Ginther called on residents to use cooling centers and swimming pools on Wednesday to beat the heat, and to check on neighbors as power slowly comes back online.
“AEP is dealing with the damage from last night’s storms plus high demand because of excessive heat. They are working to restore power to everyone. I know it’s tough – I’m without power at my house as well,” the mayor said on social media.
Records have also been hit by some power-grid operators amid the surging demand for air-conditioning. Both the Tennessee Valley Authority and Texas operator ERCOT recorded highs for electricity usage.
Schools have been forced to alter schedules due to the excessive heat. In Wisconsin, where a heat index of 108 degrees Fahrenheit was recorded by the weather service Tuesday at Milwaukee Mitchell International Airport, Milwaukee Public Schools officials dismissed students early and said they will do so again Wednesday.
“Young children and persons with certain health conditions are especially vulnerable to heat-related distress,” the district announced on its website. “For the safety of all, the district has decided to shorten the school day.”
More than a dozen schools in Minnesota that are not fully air-conditioned moved to e-learning on Tuesday, according to Minneapolis Public Schools. Detroit Public Schools announced they will close all in-person schools three hours early through Friday due to the extreme heat.
The Milwaukee County Medical Examiner’s Office said Wednesday two heat-related deaths are under investigation, and autopsy results are expected Thursday. CNN has reached out to the medical examiner’s office for additional information.
Relief may soon arrive for the Midwest as the heat is forecast to break late Wednesday, with a cold front due to bring cooler temperatures, scattered showers and thunderstorms.
Temperatures will drop to more-average levels as the front moves through Minneapolis on Wednesday afternoon and Chicago by Wednesday overnight. The cold front is forecast to move through Ohio by Thursday.
Still, even with temperatures easing a few degrees, particularly throughout the Upper Midwest, temperatures in much of the region will remain above normal, with areas of record-setting temperatures persisting into the latter part of the week.
On Thursday, temperatures are forecast to climb well above normal for much of the Great Basin, the Rockies and Southwest. An excessive heat warning has also been issued for parts of interior southern California and Arizona, where daytime highs are expected to soar once again well into the triple digits.
Don’t rely on fans to keep you cool in extreme heat. Here’s how to stay safe.
Wildfires rage in Arizona, New Mexico
Meanwhile, states across the Southwest faced an elevated risk of wildfires due to windy conditions and relative humidity on Tuesday.
In Arizona, the Pipeline Fire just north of Flagstaff has scorched more than 22,000 acres as of Wednesday morning, US Forest Service officials said. The blaze was first spotted on Sunday, according to a Tuesday update from InciWeb, a federal clearinghouse for wildfire information.
A second fire just a few miles away, the Haywire Fire, has burned roughly 5,000 acres, according to the forest service.
Firefighters in New Mexico continue to battle the two largest fires in the state’s history, the Hermits Peak/Calf Canyon Fire just northeast of Santa Fe and the Black Fire in the Gila National Forest. They have burned almost 640,000 acres combined.
There are 38 active large wildfires in the US as of Tuesday that have burned almost 1.2 million acres in four states – Alaska, Arizona, California and New Mexico, according to the National Interagency Fire Center.
CNN’s Taylor Ward, Robert Shackelford, Judson Jones, Theresa Waldrop, Andy Rose and Dave Alsup contributed to this report.