An extraordinary heat wave that’s responsible for 28 deaths in the U.S. West so far in July has hit Wyoming, and while it’s not deadly hot, it is setting records across the Cowboy State.
Communities in the western part of the state saw several record high temperatures fall Thursday as the heat system makes its way eastward, the National Weather Service reports.
The high of 96 degrees in Rock Springs on Thursday was the hottest July 11 there since 1954.
Greybull reached 103 degrees, breaking its previous record of 102 set in 2002. Meanwhile, Riverton reached 99, breaking its record of 97 degrees set in 2019. Big Piney, meanwhile, hit 93, topping the previous record of 92 set in 1948.
These were the first record-breaking high temperatures reported during the heat wave, but probably won't be the last. As the weather system moves east across Wyoming, records across the middle and eastern parts of the state also are likely to fall.
"Wyoming will get the worst of the high temperatures through Sunday," said Cowboy State Daily meteorologist Don Day. "We'll probably have an opportunity for more record-breaking temperatures between now and then."
Feel The Heat, West To East
Day pointed out a pattern in Thursday's record-breaking temperatures, which is a sign of how the heat is moving through Wyoming.
"If you look at where the records were broken yesterday, they were definitely based on the Western side of the state," he said. "Rock Springs, Riverton and Greybull were all at the edge of the heat, closer to the high pressure."
The same heat wave that brought record-high heat to Death Valley has been slowly moving across the United States.
"You'll see more of the record on the eastern side of the state Friday through Sunday," he said. "This whole airmass is moving really slow, and that's when the hottest area will reach them."
Dry Thunderstorm Danger
Multiple variables contribute to record-high temperatures, Day said.
Another important factor Thursday was that there were fewer clouds over western Wyoming, which made it feel that much hotter on the ground.
Heat waves like these tend to generate "dry thunderstorms," he said, which can bring sudden, fierce rain showers to desperately dry areas. These storms also increase the potential risk of lightning-sparked wildfires.
"Dry thunderstorms are when you get lightning but only brief periods of rain since the precipitation evaporates before it reaches the ground," he said. "The moisture level isn't adequate for the thunderstorms to produce much rain, which is a common feature in these systems."
Day said the potential for wildfires from dry thunderstorms will be "a concern" throughout Wyoming on Friday and over the weekend.
"I know there was a small grass fire west of Chugwater in the week from the lightning strike," he said. “And I would dare to say that there's a likelihood that's going to happen between now and Sunday in some areas."
Dog Days Of Summer
There is relief on the horizon.
Day expects temperatures to decrease next week, but historical statistics indicate Wyoming has just entered the hottest weeks of the year.
"Summer's maturing," he said. "The most persistent, hot weather in Wyoming usually occurs from the middle of July to the middle of August, so we're in the four-week period that is usually the hottest. This is nothing extraordinary. It's when we expect prolonged spells of hot weather."
There's more moisture in next week's forecast, which should make it cooler across Wyoming. It won't be in the 60s and 70s like during the Fourth of July, but should be noticeably cooler than last week.
Day wouldn't get into the specifics of a long-range forecast for the next few weeks, but he’s confident that the second half of July will be considerably warmer than the first half.
"If you look at the temperatures for the first nine days of July, they were far below average across the state," he said. "For the second half of July and the first half of August, I would say that that's a fairly good bet we'll have above-average temperatures."
Andrew Rossi can be reached at arossi@cowboystatedaily.com.
