An ozone health watch is in effect through Sunday night, according to the Maricopa County Air Quality Department.
The department issued the watch on Friday for Saturday and Sunday.
The health watch means the highest concentration of pollution may approach the federal health standard. Unusually sensitive people should consider reducing prolonged or heavy outdoor exertion during the period.
The department is encouraging residents to avoid waiting in long drive-through lines, unplug unused appliances, fuel vehicles after dark or during cooler evening hours and connect outdoor lights to a timer.
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