The Minnesota Pollution Control Agency issued an air pollution health advisory for the southern two-thirds of Minnesota Saturday afternoon because of elevated levels of ozone. The alert is in effect till midnight.
High ozone levels may cause respiratory distress in elderly people, children and those who exercise vigorously outdoors.
Ozone is produced on hot, sunny days by a chemical reaction between volatile organic compounds and oxides of nitrogen, the PCA said. These pollutants are released from motor vehicles, lawn and garden equipment, paints and solvents, refueling stations, and other activities that require fuel combustion.
Saturday's high will be near 93, with an overnight low of 69, according to the National Weather Service in Chanhassen.
Sunday will again be hot and sunny, with a high near 92. There's a 40 percent chance of showers and thunderstorms after 1 p.m., with storms likely overnight.
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