The state's Department of Environmental Protection has forecast a code Orange air quality action day for ozone for Friday in all regions of the state.
Friday is expected to be mostly sunny and hot, with a high near 98 degrees, according to the National Weather Service.
Ground-level ozone, a key component of smog, forms during warm weather when pollution from vehicles, industry, households and power plants "bakes" in the hot sun, making it hard for some people to breathe, according to the DEP's press release.
On air quality action days, young children, the elderly and those with respiratory problems are vulnerable to the effects of air pollution and should limit outdoor activities, according to the news release.
Officials use colors to report daily air quality. Green signifies good; yellow means moderate; orange represents unhealthy pollution levels for sensitive people; and red warns of unhealthy pollution levels for all, according to the press release.
The state recommends residents and businesses voluntarily limit pollution-producing activities and conserve energy.