It's not often you can watch Wasatch Front thermometers flutter into the upper-90s — and call that a cooling trend.

But highs on Thursday and Friday are just that, compared to the triple-digit temperatures ahead for northern Utah this weekend.

The Salt Lake and Tooele valleys combined party cloudy skies, occasional thunderstorms and rain showers with daytime highs ranging in the mid- to upper-90s on Thursday and Friday. However, clear sunny skies will usher in 101-degree highs in Salt Lake City on both Saturday and Sunday.

The National Weather Service blames that coming hotter spell — a good 10 degrees above normal — on a high pressure system and accompany warmer air mass moving into the region this weekend.

Southern Utahns, already baking in 103-105 temperatures Thursday and Friday, will see the mercury flutter to 108 degrees on Saturday in the St. George area before "cooling" to 104 on Sunday.

As for air quality, once more you might say it sucks. However, the Utah Division of Air Quality won't be endorsing any such excessive mouth-and-lip creations of partial vacuums, especially involving inhaling Utah's tainted atmosphere.

DAQ forecasters slapped "orange" grades on the state's urban valleys, declaring Salt Lake, Davis, Utah, Weber, Box Elder and Tooele counties as "unhealthy for sensitive groups" — that would be children, the elderly or anyone with compromised lung or cardiac function.

As for the remainder of the state, "yellow," or moderate ozone and particulate pollution levels will prevail through the week's end.

The Intermountain Allergy & Asthma website rated mold as "high" and plantain as "moderate" on its pollen index as of Thursday. Other allergens were either "low," or did not register.

For more extensive forecast information visit the Tribune's weather page at http://www.sltrib.com/news/weather/.

remims@sltrib.com

Twitter: @remims