A stubborn and unrelenting dome of excessive heat and humidity is languishing over the Lower 48 for the third calendar week in a row, bringing record temperatures and heat index values pushing 110 degrees in spots. Heat advisories and excessive-heat warnings blanket the northern Plains, a prelude to even more intense heat pushing into the South and Southeast.
More than 55 million Americans are predicted to face triple-digit highs this week, and overnight lows could remain in the upper 70s to lower 80s in spots. That will contribute to heat stress that could be dangerous for vulnerable populations. The National Weather Service is calling the combination of heat and humidity "extreme."
The heat, which was swelling through the Plains and Upper Midwest on Monday, is predicted to peak in the South and Southeast between Wednesday and Saturday, when high temperature records could be threatened between Central Texas and the western Carolinas.
The spiking temperatures could brew fire weather concerns amid a developing "flash drought," with scant rainfall anticipated to pose a problem for farmers.
The heat now
The heat Monday was most intense over the center of the country, including Texas, the Plains and the Upper Midwest. In North Dakota, Fargo hit 101 degrees Sunday, tying a record set in 1933, and Grand Forks made it to 100. The city will probably set a record today, too. Grand Forks is predicted to make it to 99 degrees, eclipsing the record of 98 degrees that has stood since 2010.
Aberdeen, South Dakota, is forecast to snag a 97 degree reading, and Sioux City, Iowa, should lurch to 100. Temperatures in the mid- to upper 90s are likely across most of Oklahoma and Kansas, with readings on either side of 100 degrees for the majority of Texas. Readings in the low- to mid-90s will pepper the South, but records aren't in the offing - yet.
The core of the heat shifts south and east Tuesday, allowing the northern Plains to settle back into the 80s. Temperatures in the upper 90s are likely in Chicago and Detroit, though. That could break a record in Detroit dating back to 1933.
Most of the Deep South, the South and the Mississippi Valley will peak at about three degrees warmer than Monday's highs on Tuesday. Nashville and Tupelo, Mississippi, are predicted to hit 99 degrees. Atlanta could see a high of 98 degrees, while Birmingham and Huntsville, Ala., are forecast to peak at about 97.
Record-breaking heat to come
On Wednesday, the worst of the heat wafts into the Southeast, accompanied by stifling humidity. The worst off will be Alabama, South Carolina and especially Georgia. That's where highs in a few locales could top 105 degrees, with heat indexes pushing 110.
The hottest spots Wednesday in Georgia will be around Macon and Albany, both anticipated to hit 104 degrees. In Macon, that would beat out the existing record of 101 degrees set in 1925. It would also match the 104-degree reading observed on June 15, which set a record as the hottest temperature ever observed so early in the year. Albany will probably set a daily record too.
In metropolitan Atlanta, home to about 6 million people, the high should peak at about 100 degrees Wednesday and Thursday. That would nab back-to-back records. While "Hotlanta" is accustomed to highs in the 90s, the city's characteristic sultry humidity makes it tough to nick the century mark.
The same is true in Alabama, where 100-degree readings in Huntsville and Birmingham are in the cards. Dothan may heat up to 105 degrees Thursday. Mobile is expected to get to 103 degrees, beating a record of 101 set in 2009. That will also tie as the hottest temperature for a point this early in the year.
Most of the Interstate 10 corridor will reach 100 degrees, including in Tallahassee, Gulfport-Biloxi, Mississippi, and Baton Rouge. Even New Orleans proper should hit 100 degrees Thursday and Friday, with about a 50-50 shot on Saturday and Sunday. That would net records Thursday and possibly Saturday.
Nashville will be in the upper 90s to near 100 during the stretch, and most of central and southern Arkansas should match. About two-thirds of Texas will be in the 102-to-106-degree range all the way through the weekend and into early next week.
There are no immediate signs of the heat relenting. Instead, the National Weather Service Climate Prediction Center continues to forecast odds of above-average temperatures through the end of June and perhaps into July. Warm weather and high pressure "heat domes" are a staple of any summer, but their intensity and duration are exacerbated by human-induced climate change.
Fire danger surfaces
In addition to the raw heat and humidity, which will be taxing on the human body, the extreme heat will be problematic agriculturally. Two weeks without rainfall during the summertime can easily result in "flash drought," or a sudden onset of unusually dry conditions that sap moisture from the ground. Regions beneath the quasi-stagnant heat dome, which brings sinking air and hot temperatures, will be parched as the little remaining moisture in the soil evaporates.
"Several hours of relative humidity at 25% or lower across (where 10-hour fuel moistures bottomed out yesterday at very low values of 4 to 6%) has prompted the issuance of a Fire Danger Statement for the afternoon and early evening," wrote the National Weather Service office in Peachtree City, Georgia, in an online forecast discussion.
Unfortunately, not a lick of rain is predicted anywhere in Georgia into next week.