Excessive heat warnings issued as Utah quickly jumps into 'full-blown summer'

SALT LAKE CITY — Meteorological summer began over the weekend, but it's about to feel more like mid-summer across Utah.

The National Weather Service issued excessive heat warnings for parts of southern Utah, including the St. George area and popular recreation sites like Zion National Park and Lake Powell, that will go into effect Thursday morning and last through at least Friday night.

Temperatures may reach 104-108 degrees on Thursday and Friday, while overnight lows may only drop back into the mid-70s, according to the agency. It also issued heat advisories for parts of southern and central Utah, where temperatures are forecast to reach slightly lower triple-digit temperatures.

While not quite as hot, high temperatures are forecast to reach the mid-90s along the Wasatch Front during the same time. KSL meteorologist Matt Johnson says the heat wave could break some daily record temperatures.

He explains that the temperatures are the result of a high-pressure system moving into Utah from the southwest, which will immediately bring in hotter temperatures beginning on Wednesday before the heat intensifies as it settles over Utah on Thursday.

"Thursday and Friday look like they are going to be the hottest days, then it's going to move off to the east," Johnson said.

The weather service recommends that people:

• Stay inside, preferably in an air-conditioned room. Limit strenuous activities during the middle of the day, wear lightweight and loose-fitting clothing, and drink plenty of fluids while outside.
• Do not leave young children or pets in unattended vehicles.
• Check up on relatives and neighbors who may be vulnerable to heat-related illnesses.
• Call 911 if someone is exhibiting signs of heat stroke.

Johnson said some mountain showers and thunderstorms, created by moisture coming in from the Gulf of Mexico, are possible Friday afternoon as the high-pressure system moves east.

Still, it's unclear how much relief the moisture will provide, as high temperatures near St. George are forecast to remain above or near 100 degrees through the weekend and into early next week. High temperatures are expected to reach the upper 80s and low 90s along the Wasatch Front this weekend and into next week, barring any shift in the forecast.

"We do have another round of heat that could follow sometime next week," Johnson said. "We're going to go from spring to full-blown summer here."

Streamflow impacts

The hotter temperatures are expected to lead to faster streamflows, particularly in areas where there is snowpack left over from the winter.

The Colorado Basin River Forecast Center projects that both the sections of Big and Little Cottonwood Canyon creeks at the mouth of each canyon will briefly surpass "action stage" at points this week, but it didn't expect either to hit any flooding stages as of Wednesday morning.

Both creeks are projected to get close to the listed action stage further into the Salt Lake Valley but may not reach it. The Provo and Weber rivers, within parts of the Wasatch Backcountry, and the Blacks Fork River in the High Uintas Wilderness Area are also expected to reach "near action stage" this week.

Only about 7% of Utah's above-normal snowpack is left to melt, the Natural Resources Conservation Service reported Tuesday afternoon. Almost all that is left is in the Wasatch and Uinta mountains, as well as the mountains near Beaver.

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

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