With temperatures expected to reach the lower 90s amid high humidity, the heat index could approach the triple digits on Wednesday in Baltimore.
A "Code Orange" air quality alert is meanwhile in effect because of the heat and lack of wind. That means air pollution is expected to reach unhealthy levels that could bother sensitive groups, including children, the elderly and those with heart or lung conditions.
Highs are forecast to reach about 92 degrees in the Interstate 95 corridor. With dew points at or above 70 degrees -- a level that indicates very humid and uncomfortable conditiosn -- that is expected to make it feel like the upper 90s.
At 1 p.m., it felt like 94 degrees at Baltimore/Washington International Thurgood Marshall Airport. The air temperature was 89 degrees with a dew point of 69 degrees.
There is a slight chance the heat and sunshine could spur thunderstorms in the afternoon and evening.
More heat is forecast into the weekend, with highs in the mid-90s Thursday, Friday and Saturday expected. "Code Orange" conditions are forecast through the week.