Excessive heat warnings issued throughout Utah as ‘heat dome’ arrives

A “heat dome” that has generated record-breaking temperatures throughout the West over the past few days is now making its way to Utah, where it’s expected to boost temperatures close to some of the hottest ever recorded in the state.

The National Weather Service has issued a series of excessive heat warnings and watches throughout most of Utah, where triple-digit temperatures are expected across nearly all valley communities Wednesday through the end of the week.

The alerts advise:

• High temperatures are expected to reach between 100 and 107 degrees throughout most areas in the state, including the Wasatch Front. Overnight lows may remain in the mid- to upper-70s.
• For locations in and around St. George, which reached 114 degrees Monday, temperatures are expected to remain between 110 and 115 degrees, while overnight lows are forecast to stay in the upper 70s and low 80s.

There's also some variability with the temperature, meaning highs could end up slightly higher or lower than what's forecast if the right conditions set up. That means the system could match or break some of the state's all-time high-temperature records, says KSL meteorologist Matt Johnson.

"They might make a run for their highest recorded temperature," he said, pointing to St. George.

St. George's all-time record high is 117 degrees, which is also the state's all-time hottest temperature, set in 1985 and matched three years ago. Salt Lake City's all-time record is 107 degrees, which has been recorded five times since 1874.

The 'heat dome' arrives

The incoming heat wave comes after a particularly hot start to summer. Last month was Utah's third-hottest June since 1895, according to National Centers for Environmental Information data released Tuesday. It was the second-hottest June on record in Salt Lake City.

July has been off to a cooler start, at least along the Wasatch Front where cooler air has kept Salt Lake City's temperatures nearly three degrees below normal during the first week of the month. But that is set to change with the strong high-pressure system, also known as a "heat dome."

It has already shattered daily and all-time temperature records across the West. Most notably, it sent temperatures soaring to 120 degrees in Las Vegas for the first time ever on Sunday. It also reached 129 degrees at Death Valley National Park, one degree off its all-time record in the reliably measured temperatures era.

There are two high-pressure systems in the West; the core of the southern one is causing Utah's temperatures to rise before it even reaches the state, Johnson said. High temperatures could return to triple digits in parts of the Wasatch Front on Tuesday, even before all the excessive heat warnings go into effect.

Triple-digit heat is forecast to linger along the Wasatch Front through at least Sunday, while temperatures are expected to remain above 110 degrees in and around St. George until about Saturday.

Weather models show the system will move over southwestern Utah by Thursday, which is expected to be the hottest day of the week. That's when Utah's all-time record highs could be challenged, but daily records are forecast to be broken over the next few days, as well.

Beating the heat

The excessive heat can be deadly, which is why the National Weather Service recommends:

• Limiting time outdoors during the heat of the day, if possible. Stay in an air-conditioned room and out of the sun.
• If outdoors, drink plenty of fluids, wear lightweight/loose-fitting clothing and limit "strenuous activities" to early morning or evening.
• Take action when you experience or see symptoms of heat exhaustion and heat stroke. Call 911 and move a person to a cooler area if they are showing signs of heat stroke.
• Never leave young children or pets in unattended vehicles.
• Check on relatives and neighbors, especially those who may be prone to heat-related illness.

Some communities have opened "cool zones" for residents who don't have air conditioning. Salt Lake County, for example, has an interactive map showing which areas open to the public during extreme heat.

Relief in sight?

Some relief could arrive as early as this weekend, though.

Johnson said models show monsoonal moisture may make its way into Utah this weekend, which could provide some scattered showers and help lower temperatures — at least out of the record range.

The probability of rain begins to pick up early next week. Updated long-range forecasts list southeastern Utah as having the highest probability of above-normal precipitation in the state next week.

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