Heat advisories and excessive heat warnings blanket the Plains, where the combination of record-challenging heat and tropical humidity will place dangerous amounts of strain on the human body for those who can’t escape the heat. That presents a serious threat to the elderly, homeless individuals and others without adequate access to cooling shelters.
“Extreme heat and humidity will significantly increase the potential for heat related illnesses,” wrote the National Weather Service, “particularly for those working or participating in outdoor activities.”
The heat is centered over the southern Plains and south-central United States, but it has already managed to deliver a record temperature of 107 degrees to Salt Lake City on Sunday. In Montana, Glasgow experienced one of its 10 hottest days on record at 108 degrees.
A sprawling ridge of high pressure known as a heat dome is responsible for the high temperatures. It brings clear skies, sinking air and abundant sunshine. It also shunts the jet stream north into Canada, deflecting any major storm systems or inclement weather. That’s why heat domes often beget drought.
Tuesday is likely to be the hottest of the next week, though highs over the century mark will linger for the forecastable future. Oklahoma City is projected to hit 109 degrees Tuesday, the hottest since July 20, 2018. The Sooner State’s capital has hit 109 degrees only 19 times since 1890.
“We had one day in 2018 where we made it to 109,” said Vivek Mahale, a meteorologist with the National Weather Service in Norman, Okla. “We’ll be around 104 tomorrow [Wednesday], but even so we’re going to be 5 to 7 degrees above average through the rest of this week.”
In southwest Oklahoma along the H.E. Bailey Turnpike, the high temperature is slated to peak at around 112 degrees Tuesday afternoon. Since July 1912, that’s happened only 20 times — making the heat a roughly once-in-five-year event.
It’s a similar story in Wichita Falls, just across the Red River in north Central Texas, where a 112 degree reading is also projected.
The extreme heat, locally topping 110 degrees, bleeds farther south toward the Dallas-Fort Worth Metroplex, where DFW International Airport tied for its hottest day on record Monday. The morning low of 86 degrees and the afternoon high of 109 averaged to 97.5 degrees, matching the record set on Aug. 3, 2011. That 86 degrees also tied for a record warm low.
Fort Worth’s Meacham International Airport spiked to 110 degrees Monday.
Dallas is predicted to hit 109 again Tuesday and 108 on Wednesday. So far this month, DFW has already had 14 days at 100 degrees or more.
🌡️Dangerous heat is expected on Tuesday with near record temperatures. Forecast highs range from 106 to 113 °F.
— NWS Norman (@NWSNorman) July 18, 2022
In addition to the magnitude of the heat, the duration is equally alarming.
“I’d say right now the longevity” is most impressive, Mahale said. “The biggest impact to people is how persistent it’s been.”
The heat itself is unusual — about 5 to 10 degrees above average in places like Oklahoma and Kansas and up to 15 degrees hotter than typical in the Lone Star State. Even Houston is expected to peak around 100 degrees each afternoon through at least the start of next week.
In Austin, highs in the 102 to 106 degree range are expected through at least the start of next week. The same is true in San Antonio, Tulsa and Wichita.
Even more problematic are nighttime lows, which in many areas will not dip below the mid-80s. Hot overnight temperatures are major contributors to heat-related fatalities, since warm nights prevent the body from entering its nocturnal cool-down period. Highs above 100 degrees will extend throughout the Desert Southwest too.
The sun is setting on an intense brush fire in Somervell county (SW of DFW). This fire is producing a tall pyrocumulus cloud (see its shadow on the east side). Fire releases heat & moisture and when unstable atmospheric conditions exist, these can grow into storms.#dfwwx #txwx pic.twitter.com/ueHaQsTqxE
— NWS Fort Worth (@NWSFortWorth) July 19, 2022
In Southeast Texas and along the Gulf Coast, dew points near 70 — indicating the amount of tropical moisture in the air — will lead to heat indexes approaching or exceeding 110 degrees. Farther north and west over the Interstate 35 corridor, comparatively less moisture will translate to fire weather concerns. Red flag warnings are up for a wide swath of Texas and Oklahoma, where relative humidity could fall below 25 percent and winds may gust up to 30 mph.
“A red flag warning means that a dangerous combination of weather conditions and dry vegetation is expected within 24 hours, favoring rapid growth and spread of any wildfires,” wrote the National Weather Service in Tulsa. Several fires are already burning across the south-central Plains.
Those conditions could “contribute to extreme fire behavior,” echoed the Weather Service in Norman. More than half of Texas is experiencing a severe or top-tier “exceptional” drought, according to the U.S. Drought Monitor.
“We haven’t had substantial rainfall for a little while,” Mahale said. “A lot of our stations haven’t had rainfall of at least a quarter-inch for 30 to 40 days, and only isolated to widely scattered storms for the past month. As vegetation dries out, that makes it easier for the crops to heat up. You don’t have much evapotranspiration going on, and things dry out.”