BUFFALO, N.Y. (WIVB) — Air quality in western New York, and much of the rest of New York State, is expected to be poor on Wednesday through much of the day.

New York State Department of Environmental Conservation officials issued an Ozone advisory, saying pollutants are expected to exceed an Air Quality Index value of 100, potentially threatening the health of more vulnerable New Yorkers.

Officials say heat will cause the formation of ground-level ozone, which creates photochemical smog. The true source of the pollutant typically is out of state emissions and vehicle exhaust.

When values are high — as they are expected to be on Wednesday throughout the day until nightfall — residents who vigorously exercise or work outside, or have conditions related to breathing, like asthma, should stay indoors when possible.

In order to reduce ground-level ozone, residents can use mass transit or carpool rather than drive, turn off unneeded drains on electricity when not in use and use fans to circulate air over air conditioning.

In addition to all western New York counties, counties in and surrounding New York City are expected to be impacted.

The advisory will last from 11 a.m. through 11 p.m.