For the second day in a row, high temperatures, still air and a swath of pollution stretching to the Ohio Valley are forecast today to give Maryland some of the East Coast's least healthy air.

Ozone pollution, the main ingredient in smog, climbed to "code red" levels in parts of Anne Arundel, Baltimore and Cecil counties yesterday. "Code orange" pollution covered the rest of Central Maryland and the entire Eastern Shore, according to an Environmental Protection Agency computer simulation.

Code red levels are unhealthy for everyone; code orange are potentially harmful for children, the elderly and people with respiratory problems. State officials issued a pollution alert yesterday, when high temperatures reached the 90s, urging that children stay inside and adults limit outdoor exercise. The same warning is in place for today.

University of Maryland air-quality forecaster Charles Piety said a high-pressure system has trapped a "finger of haze" reaching from the Ohio Valley, holding it over Maryland and Pennsylvania. In light winds, "the dirty air just slops around, and that's what we think is going to happen," he said.

Storms are expected to wash away the haze tomorrow. The state Department of the Environment is asking to help keep ozone levels down by limiting driving, postponing lawn mowing and refueling cars after dark.