Fires to the north, in Nevada and Idaho, and south, near Milford, sent soot to the populated Wasatch Front and threatened to keep the smoke coming as long as they continue burning the next few days.

While temperatures are expected to inch up day by day through the week, and while the landscape remains dry as tinder and humidity stays dangerously low, the winds that fueled the fires and carried the smoke to the Wasatch Front are expected to die down, said Larry Dunn, meteorologist-in-charge at the Salt Lake City office of the National Weather Service.

"There's nowhere else for the smoke to go," he said.

As of Sunday evening, ozone and fine-particle pollution remained below federal health standards. But it had been climbing through much of the day, as Wasatch Front residents couldn't avoid noticing with a thickening haze.

Dry lightning continues to be a threat today in mountain areas, including the northern Wasatch and Uinta mountains and the area north of Cedar City, where firefighters are battling the Milford Flat blaze.

Temperatures dipped a few degrees on Sunday - a welcomed relief from nearly two weeks of temperatures of around 100 degrees. Sunday's temperature at the airport was 96 degrees, 5 less than the 101 recorded on Saturday.

Salt Lake City's temperature is expected to reach 98 today. In St. George, temperatures approaching 110 are projected.

Fires dump lots of soot into the air, soot that is typically associated with the wintertime inversions so familiar to northern Utahns. Wildfires also pump lots of mercury into the air.

In addition, the soot reacts with other chemicals and, with a little stewing by the heat and sun, boosts levels of Utah's common summertime pollutant, ozone.

The air-quality forecast for northern Utah is red for the next few days, according to the Division of Air Monitoring. People in sensitive groups - the old, the young and people with heart and lung problems - are urged to limit prolonged and heavy exertion.

Joggers and others who enjoy outdoor activities may want to shift their workout times to the mornings, when pollution levels will be lowest.

And people can help keep the air clean by using their cars less and taking other steps to reduce pollution.

More online

Pollution reduction tips can be found at www.cleanair.utah.gov.