The Evansville EPA and Vanderburgh County Health Department have issued an Ozone Alert for Saturday.
The combination of bright sun and little or no wind could cause ozone levels to reach or exceed unhealthy levels for sensitive people.
The agencies are warning people with heart or lung disease, children, and older adults to reduce prolonged or heavy exertion outdoors, especially between noon and 7 p.m. when ozone levels are highest.
Exposure to high levels of ozone can cause lung and throat irritation, shortness of breath, and aggravate respiratory diseases such as asthma, emphysema, and bronchitis.
Open burning is prohibited during the alert, but outdoor cooking is permitted. Officials urge residents to postpone grilling until after 7 p.m.
Residents are also encouraged to conserve electricity, use public transit or limit driving, and postpone refueling vehicles until the evening.
The agencies recommend using electric or manually-operated lawn equipment, and limit the use of cleaning fluids, paint thinners, or other materials containing volatile organic compounds during the alert.