Another steamy day is on tap for Philadelphia-area residents, who can expect more heat, humidity and possible thunderstorms.

High ozone levels have also caused the environmental protection departments in Pennsylvania and New Jersey to issue air-quality alerts.

The "code orange" alert means pollution levels are expected to unhealthy for sensitive groups, like young children, the elderly and those with asthma, emphysema or bronchitis.

The alerts cover Philadelphia, its suburban counties in Pennsylvania and most of New Jersey.

Ozone is forecast to reach unhealthy levels across New Jersey "due to southwest winds, sunny skies and hot temperatures," according to Air Now, the Environmental Protection Agency's air-quality website.

The high temperature today in Philadelphia is expected to reach 91 degrees, the National Weather Service says.

There's a chance of showers and thunderstorms, especially between 2 p.m. and midnight, forecasters say.

That comes after Monday recorded high temperature of 92 degrees, and the region will remain "locked in a hot and humid airmass through at least the end of the work week," according to the weather service.

Highs of 92 and 90 degrees are forecasted for Wednesday and Thursday, respectively. Scattered thunderstorms are also expected both days.

A cold front is expected to move through the region Friday. Temperatures Friday and over the weekend should be cooler than the work-week highs.