Incoming ‘heat dome’ expected to push Utah temperatures close to all-time record

A “heat dome” setting up over West is creating temperatures hot enough to potentially threaten the highest temperature ever recorded in Utah if the right conditions line up.

The National Weather Service on Friday issued a series of excessive heat warnings for parts of southern Utah, including low-elevation communities in Washington County, as well as low-lying areas of Zion National Park and Glen Canyon National Recreation Area, that will run from Sunday through at least Tuesday.

Federal forecasters currently project that high temperatures will reach or exceed 110 degrees in St. George beginning on Saturday. That's expected to continue through at least the middle of next week with the potential of reaching 114 degrees on Tuesday. Temperature forecasts could change as the high-pressure system gets closer to Utah, meaning hotter or cooler temperatures are possible.

But the current projection isn't far from the hottest temperature ever recorded in Utah, which remains 117 degrees. The temperature was first recorded in St. George exactly 39 years ago on Friday and then matched in July 2021 .

What's causing the heat?

The incoming heat wave is tied to a strong high-pressure system set up over the California coast on Friday, says KSL meteorologist Matt Johnson. This pattern is expected to create a heat dome.

A heat dome, the Associated Press explained last month , is created when the air below the high-pressure system sinks and compresses, raising ground temperatures and creating a "bulging dome." Johnson says systems like this that form over the Pacific are typically hotter than those generated from the Gulf of Mexico because there's less moisture near it.

In this case, the system is large enough that excessive heat warnings and watches, and heat advisories are in place throughout most of California, Oregon and Washington, as well as the western halves of Arizona, Idaho and Nevada.

"It's an expansive high-pressure system — definitely large in size — and it's also packing a lot of hot air in it," Johnson said.

One of the warnings says temperatures may reach 129 degrees at Furnace Creek within Death Valley National Park over the weekend, which puts it within range of potentially matching or topping a major record.

As KTLA points out , 130 degrees is the highest "reliably measured temperature" ever recorded on Earth. The outlet notes that there have been hotter temperatures beyond 130 degrees, but many experts are skeptical about those readings over the quality of instruments used in the past.

Meteorologists from the National Weather Service's Las Vegas office told USA Today on Thursday that there's about a 20% probability that temperatures will reach 130 degrees at Furnace Creek on Monday and Tuesday as the high-pressure system lingers in the region.

"This heat is very dangerous," the agency wrote in a social media post on Wednesday. "Yes, the Mojave Desert gets hot; but this heat will be record-breaking."

Utah heat wave

The high-pressure system will eventually arrive in Utah, but it's "taking its sweet time" rolling in, Johnson says. Its core will move over northern California on Saturday before jutting southwest toward central California and Nevada this weekend. It'll eventually set up over southwest Utah before moving out next week.

Its delay will benefit Utah's northern half. Dry and cooler Canadian winds are bouncing around the high-pressure system and into Utah instead. These northwest winds are forecast to remain a fixture along the Wasatch Front this weekend and into early next week, keeping highs in the low- to mid-90s through the next few days.

Southwest Utah isn't getting this same benefit, which is why temperatures could reach 110 degrees by as early as Saturday. Temperatures will increase in the region as the core of the high-pressure system arrives early next week; triple-digit temperatures are expected to return along the Wasatch Front by midweek because the northwest winds will die off.

"What we're expecting is a four- to five-day stretch of triple-digits here in the Salt Lake Valley and most of the Wasatch Front," Johnson said. "Down south, as Washington County sits closer to the core of this high-pressure system, their heat is going to be a little bit extreme and potentially record-breaking."

He adds he believes Utah's all-time high temperature won't be tied or broken, but it's not off the table. Dry soil moisture levels are typically a key factor in record-breaking heat and soil moisture levels were much drier in 2021 than they are now.

"It almost feels like anything's possible these days, so you can't rule it out, but I lean away from an all-time high simply because you still have decent moisture in the soil," he said.

It's unclear how long the heat wave will last, but long-range models indicate that relief is on the way. The National Weather Service Climate Prediction Center projects wetter-than-normal conditions emerging in Utah toward the end of next week into the ensuing week. Higher probabilities are closer to Arizona, indicating a monsoon-like pattern potentially setting up.

That's something that meteorologists will track in the coming week.

Full seven-day forecasts for areas across Utah can be found online, at the KSL Weather Center .