Today threatens to be the fifth straight day of 100-degree-plus temperatures for northern Utah.

To add to the misery, today also should be another "red alert" day for unhealthy levels of ozone air pollution in Salt Lake, Utah, Davis and Weber counties, according to the Utah Division of Air Quality.

People with heart or respiratory ailments should reduce outdoor activity during times of heaviest ozone concentrations, during the midmorning and afternoon hours.

"This is a long hot spell," said Robert Dalley, manager of the division air monitoring center. "Red alert" days also were recorded Friday and Sunday, he said late Monday.

A "red alert" could also be issued for Wednesday, he said.

At such times, state experts ask that residents consolidate car trips. They should postpone mowing the lawn until the concentrations are better. Also, because ozone can harm lungs, people should exercise in the morning, when concentrations are lower.

The heat is so bad in southern Utah that St. George police said they will break car windows and extract youngsters or pets left inside.

"If we see an animal or child that is in distress at all, we will break the window immediately," St. George Police Sgt. Craig Harding said Monday. "We will either arrest or cite the individual for animal cruelty or child abuse or child negligence.

"We don't give warnings."

Officers will simply smash the window because time is crucial to life or health. The car's owner will be responsible for repairing the damage.

Last year, he added, officers responded to a call about an animal or child left alone in a hot car "about once a month" during the sweltering summer. This week, temperatures have soared higher than 110 degrees at St. George.

In 2005, after rescuing two children from a hot car in a store parking lot, police placed a meat thermometer on the seat of Harding's police car and left it for an hour on a day when the outside temperature was 108.

"It was over 175 degrees inside my car," Harding said. "The thermometer was sitting in the seat where the child would be sitting."

Utah's soaring temperatures are not affecting the delivery of electricity to customers of Rocky Mountain Power (formerly known as Utah Power), which supplies 75 percent of the state's electricity.

According to utility spokesman Dave Eskelsen, several small outages occurred on Monday across the state, including one in Kearns, which shut off power to nearly 300 customers. Other temporary outages occurred in Cedar City — which affected 84 customers — and in Farmington and Evanston, Wyo.