Just when it seems Wyoming has hit its boiling point with 100-degree temperatures in some spots, a cold front from Canada will cool things off in a big way Thursday and Friday.
The cold front started moving across northwest Wyoming on Wednesday and will shock people’s summertime systems with daytime high temperatures plunging anywhere from 10-30 degrees, depending on where you are in the Cowboy State.
"Right now, we have a high in Cheyenne of 58 degrees on Thursday, which is well below average for this time of year," said Shelby Fuller, a meteorologist with the National Weather Service (NWS) office in Cheyenne. "It will be pretty overcast for much of the day tomorrow as well, keeping those temperatures cool and below average."
Temperatures across the rest of Wyoming won't drop as drastically, but Thursday will be noticeably cooler.
"We're looking at highs in the mid and upper 80s between the Bighorn Basin and Casper on Wednesday," said Celia Hensley, a meteorologist with the NWS office in Riverton. "By tomorrow, temperatures will be in the low 70s across the Wind River Basin, and Casper might not even reach 70."
The cold front from Canada won't last long, and the summer heat will return by next week. Still, that's quite a day-to-day drop for the Cowboy State.
Alaska Summer
The northern cold front is a taste of what summer’s like in the far north of North America. A high-pressure system descended on Alaska earlier this week, displacing the cooler air in the region and sending it southward toward Wyoming.
This cold front is coinciding with the next wave of subtropical moisture. Cowboy State Daily meteorologist Don Day said there's a decent chance that parched regions of Wyoming will get some much-needed rainfall Thursday and Friday.
"If you were to draw a line from the northern half of the Bighorn Basin to Sheridan and Buffalo, then Casper to Cheyenne, the eastern side of that line is where the best chances of rain will be through Friday," he said. "That's where the cold air will work with the subtropical moisture to give the eastern counties of Wyoming a good chance of rain."
Platte County falls on the eastern side of that line, which gives it a better chance of rainfall. That will be good news for Hartville and Guernsey as they battle the Pleasant Valley fire, which has burned nearly 29,000 acres and is now 100% contained.
Meanwhile, western Wyoming won't see much moisture Thursday and Friday. Day said the probability of precipitation will increase on both sides of the Continental Divide over the weekend.
"The western side of Wyoming isn't going to see much through Friday," he said. "There will be a little bit of shower and thunderstorm activity, but the western side of the state will get into a pretty good chance of afternoon showers and thunderstorms this weekend. The entire state is going to get into the mix, but it's east of the Continental Divide first, then both sides of the mountains Saturday and Sunday."
The main hazard of this potential deluge of cooler rain showers is the chance of flash flooding once the cold front arrives. Fuller cautioned southeast Wyoming residents to be aware of sudden, severe thunderstorms that could turn trickles into torrents.
"The biggest hazard would be Wednesday afternoon and evening," she said. "You could see a couple of severe thunderstorms, a threat of high winds and potentially quarter-sized hail as well as heavy rain. If a storm lingers over an area for a while, it could lead to some flash.
“But we're not really looking at too big of an impact (in southeast Wyoming) on Thursday and Friday. Maybe some showers, but not looking at anything severe at the moment."
Not-So-Unprecedented
Daytime highs in the 70s will be a welcome relief from the sweltering summer temperatures felt throughout Wyoming the last few weeks. Day conceded that it has been hotter than average this summer.
"I hear this every year," he said. "Looking at the last 60 days, roughly June 5 to Aug. 5, most of Wyoming has had above-average temperatures by anywhere from about 1 to 3 degrees Fahrenheit."
However, this comes with caveats. While Summer 2024 is hotter overall than Summer 2023, which was cooler and wetter than normal, Day didn't have to look far into Wyoming's past to find a precedent for this summer's temperatures.
"Summer 2022 looks exactly like summer 2024," he said. "They are about the same, about 1 to 3 degrees above average. People tend to be biased to what has happened the most recently, but this isn't the hottest summer we've ever seen. The data just doesn't add up."
Summer 2023 was cooler overall, but that was from above-average moisture maintaining below-average temperatures. Day believes short memories have contributed to the exaggerated claims of Wyoming's summer heat.
"There's a pretty big contrast between the cool, wet summer of 2023 and the hotter, drier summer of 2024," he said. "From this year to last, there's as much as six degrees difference in some regions of Wyoming. That contrast between one year to the next is going to be noticeable, without a doubt. But that doesn't necessarily mean we've never seen a summer this hot before."
Short Fall, Then Back To Summer
While the northern cold front will contribute to a cooler Thursday and Friday, its impact will be gone by the beginning of next week. Monday's daytime highs will return to the average summertime temperatures expected for mid-August in Wyoming.
"The monsoonal moisture will help keep things a little cooler over the weekend," Hensley said. “But we'll have persistent temperatures in the mid to upper 80s by the end of the weekend. It has seemed very warm all summer, so I'm looking forward to the cooler temperatures, and it'll be a welcome relief for many others."
Cold fronts like this aren't unprecedented for mid-August but tend to happen closer to the end of August and the beginning of September. That's when the fronts signal seasonal change, but there's still plenty of summer heat to come in the Cowboy State.
"That's just our Wyoming weather," Fuller said. "You go from blistering hot one day to chilly the next day. This cold front will definitely be a good break from the 90-degree temperatures we've been seeing lately, but our temperatures will bounce back to near-average by Monday."
Andrew Rossi can be reached at arossi@cowboystatedaily.com.
