Chicago may hit century mark for 1st time in nearly 10 years

Since the start of June, large portions of the central and eastern United States have been able to enjoy rather seasonable conditions, but AccuWeather forecasters say comfortable weather will be but a distant memory in the days to come.

A drastic and intense warmup is on the way for a large swath of the country this week as a major atmospheric feature shifts position.

"As the jet stream lifts north, a large heat dome will become more expansive over the Central states, Midwest and Southeast over the next several days," AccuWeather Senior Meteorologist Dan Pydynowski explained.

Last week, a large swath of the United States roasted amidst unseasonable heat as high temperature records shattered from the Southwestern states to Texas. The same feature that brought sweltering heat to those regions will now allow Mother Nature to crank up the thermostat for another part of the country.

From Monday through Wednesday, high temperatures will soar 10-20 degrees Fahrenheit above normal as July-like air engulfs areas from the Plains to the Midwest and even parts of the East Coast. Depending on location, the day of peak heating will vary, but the unseasonable aspect of the heat itself will remain consistent through at least midweek for many areas.

"Cities such as Chicago, St. Louis and even cities as far east as Charlotte and Raleigh, North Carolina, will be flirting with record high temperatures and triple-digit readings several days in a row this week," Pydynowski said.

Unseasonable heat will begin in earnest by Monday for many locations from the central Plains to the Midwest.

On Monday, residents of places such as Wichita, Kana., and Kansas City, Mo., will likely experience the worst of the heat this push has to offer. High temperatures in both cities typically top out in the middle 80s F at this time of year, but by Monday, both are forecast to top out within a degree or two of 100 F.

By Tuesday, heat will peak in places like Chicago and Indianapolis. High temperatures around 80 F are typical for both metros in mid-June, but the mercury in both cities will skyrocket to just shy of 100 F on Tuesday.

Heat on Tuesday will sizzle across the entire greater Chicago metro, but areas closest to the Lake Michigan shoreline may end up a few degrees lower than areas farther inland.

At Chicago O'Hare International Airport, one of the official weather reporting locations for the area, the high temperature is forecast to reach a staggering 99 F on Tuesday. The last time O'Hare recorded a day with a temperature higher than 99 F in June was all the way back on June 28, 2012, when the mercury soared to 100 F.

In fact, the last time Chicago eclipsed the century mark at all was July 6, 2012, when the city topped out at 103 F.

If Chicago records a temperature of 100 F or more at all, it typically does not occur until the middle of July. Tuesday's high temperature for the city could flirt with that triple-digit benchmark and could become one of the top two or three earliest readings of all time and the first reading in nearly a decade.

Like Chicago, St. Louis is a relative stranger to temperatures in the triple digits. Since 2018, the city has recorded only three days when the mercury hit 100 F or more, according to AccuWeather Meteorologist Matt Benz.

"This week, St. Louis is forecast to record high temperatures of 100 F or more from Monday to Wednesday," Benz added. "If so, this would match the total number of 100-degree days since 2018."

Outside of the Midwest, Tuesday is also set to be generally the hottest day of the week for large portions of the Southeast.

Charlotte, N.C., is forecast to top out at 101 F on Tuesday which would break a decades-old record. The current daily record for June 14 stands at 99 F from 1986. Raleigh will also flirt with record temperatures through midweek.

By Wednesday, the core of the heat will slowly slide farther east, but relief will be limited for the Central states. Much of the Plains will remain upwards of 10 degrees above normal by midweek.

The shift and ultimate eastward expansion of the heat Wednesday will put places like Cleveland and Pittsburgh fully in the mix to bake under the worst heat of the week. Both cities will flirt with record high temperatures on Wednesday as temperatures top out upwards of 15 degrees above average for mid-June.

In addition to record-challenging temperatures during the daytime hours, temperatures will also remain elevated during the overnight hours for much of the week. Through at least Wednesday, residents across the Midwest and portions of the East without access to air conditioning will struggle to cool off overnight.

"The overnight hours, when temperatures are expected to drop to the daily minimum, can become a secret danger to residents during a heat wave," AccuWeather Meteorologist Alyssa Smithmyer said. "When the air temperatures remain at elevated levels as people go to sleep, additional strain to the heart can occur as the body tries to regulate the internal temperature."

This phenomenon is especially pronounced in highly-urbanized areas subject to the urban heat island effect. Metropolitan areas often have a high density of buildings and roadways that are constructed with materials that are not quick to release heat and therefore do not cool down quickly at night.

Heat will linger across many of the affected areas into the end of the week, but the extremity of the heat will begin to temper somewhat from midweek onward.

"Finally, by late in the week, a cold front will trim back the heat and bring some relief to portions of the Midwest and Great Lakes," Pydynowski said.