Mandatory bans on solid-fuel burning devices and open burning were in place, and motorists were asked to reduce trips, avoid idling or opt for mass transit. Industrial businesses were urged to optimize their operations with an eye toward limiting their emissions.
The elderly, very young and those with heart or respiratory conditions should avoid outdoor activity in the affected areas, especially during peak-pollution periods in the mid-morning and afternoon hours.
The record-setting pace of cold temperatures was fading with slight warming, but it remained abnormally chilly in Utah. On Wednesday, the Utah Test and Training Range dipped to minus 5, beating a 1999 record low of 6 degrees; Bullfrog Marina, on Lake Powell, recorded an 11, a degree colder than its old 1978 record of 12.
On Friday, the Wasatch Front looked for daytime highs in the upper-20s and overnight lows in the 5-10 degree range. That forecast was a twin for the one on Thursday.
Southern Utahns were to warm into the mid-30s with overnight lows in the low-20s.
A storm expected to move into Utah Friday had lost much of its punch as it moved from the Pacific inland. On Thursday, the National Weather Service said it would not budge the inversions plaguing the state's population centers.
There also was some modest improvement in the risks for potentially deadly snowslides in Utah's mountain backcountry: While Ogden, Salt Lake, Provo and the Unitas districts remained at "considerable" levels, the mountains of Logan and the Skyline district were at "moderate" as Thursday dawned, according to the Utah Avalanche Center.
For more extensive forecast information, visit the Tribune's weather page at sltrib.com/weather.