While inducing spring fever across the region, the heat wave also provoked something previously unknown in mid-April: an ozone alert.

The weather report on the radio or TV tells you that it is going to be sunny and hot and that an orange ozone alert has been issued.

In Denver, the State Health Department issued an ozone alert and warned people with respiratory conditions to remain indoors as acrid smoke and ash blew over the area.

At noon on Sunday, Aug. 6, the traffic was at a near standstill for a great distance from the toll booths in both directions, aggravating conditions that led to the ozone alert.

So were visits to the emergency rooms of the 11 acute-care hospitals operated by New York City, particularly by people with asthma and other respiratory ailments, as the city endured its third day of an ozone alert.

Ozone Action Days, alternately called an "Ozone Alert" or a "Clean Air Alert", primarily center in the midwestern portion of the United States; particularly in well-urbanized areas such as Chicago, Cleveland, Detroit, and Indianapolis.