The heat is on.
The National Weather Service issued an excessive heat warning for parts of southwest and south-central Utah that will take effect Saturday afternoon and remain in place through Monday evening.
The agency also issued an excessive heat watch for areas along the Wasatch Front, Tooele and Rush valleys, and the West Desert. That will take effect Sunday afternoon and remain in place through Monday evening.
The warnings and watches are because of extreme heat that is expected as a result of a pair of high-pressure systems that will "combine forces" over the region, says KSL meteorologist Matt Johnson.
One of the systems is currently over New Mexico and Texas, while the other is just off the Pacific Coast in Southern California. Johnson said there will be some "slight cooling" in northern Utah on Thursday and Friday as the former moves west toward California because it will send in cooler winds from the north. But high temperatures will only drop about 5 degrees from the highs over the past few days.
The combined high-pressure system is forecast to bounce back over Utah this weekend, settling over the St. George area by Sunday.
"It will be blazing hot ... flirting with all-time record highs this Sunday in St. George," Johnson said. "As that high is right overhead, we're experiencing temperatures in the low 100s, potentially around 104 (degrees) in Salt Lake City."
Johnson said Monday will remain hot across the state, but not as hot, as the high-pressure system begins to move southeast back toward Arizona and New Mexico. The forecast calls for more cloud cover to return Monday with the system moving out.
The weather service advisories note that high temperatures are projected to reach as high as 115 degrees in Washington County and areas near the Glen Canyon National Recreation Area. The state's all-time record high is 117 degrees set in 1985 and matched in 2021. Both of those occurred in St. George.
High temperatures could reach up to 104 degrees between Sunday and Monday within the section of northern Utah included in the excessive heat watch. Salt Lake City's record high is 107 degrees, matched multiple times over the last few years.
"Extreme heat will significantly increase the potential for heat-related illnesses, particularly for those working or participating in outdoor activities," the weather service says. "Drink plenty of fluids, stay in an air-conditioned room, stay out of the sun, and check up on relatives and neighbors."
Overnight lows are projected to remain in the mid-to-upper 70s across the state.
Johnson said the potential for storms to return increases Monday and Tuesday, which are tied to moisture "on the back side" of the high-pressure system moving out of Utah.
Full seven-day forecasts for areas across Utah can be found online at the KSL Weather Center.
