The second day of the week's heat wave reached the low 90s with poor air quality, and conditions are expected to continue through the weekend.
The high temperature at Baltimore-Washington Thurgood Marshall Airport was 92 on Thursday, below the 2011 record of 98.
The hot weather will stay about the same throughout the week, with highs reaching 92 to 96 degrees and the possibility of isolated showers and storms in the evenings, according to the National Weather Service. The heat wave and high pressure will remain until Sunday night or Monday morning, when a slow-moving cool front is expected to arrive.
A Code Orange air-quality level is forecast again for Friday by the Metropolitan Washington Council of Governments and Maryland Department of the Environment, meaning pollution levels can be harmful to children and those with health problems.
People with "respiratory concerns such as the elderly and small children should stay out of the heat, specifically between 11 a.m. and 2 p.m.," said NWS meteorologist Kevin Witt.
The summer-like temperatures triggered the opening of cooling centers in Carroll County on Thursday and Friday, while other localities recommended that residents exercise caution.
Marylanders and visitors responded differently to the change in temperature. Fort McHenry park ranger Tim Ertel watched the visitors closely Thursday to make sure they stayed hydrated, particularly the tourists who aren't used to sporadic Baltimore conditions. "We will probably be wearing sweaters this weekend, but if you don't know that it goes from 40 to 90 here, you can be caught off guard."
Members of a school group from Fullerton, Calif., on a weeklong East Coast history field trip, wore bright blue long-sleeve jackets for easier identification. The heat surprised them, and by the end of the visit, many were sweating, with jackets tied around their waists.
Another touring student, Brandon Johnson, 14, from Chester Springs, Pa., said he was "not dealing with the heat well." His classmate Luke Switek said jokingly, "I never thought I'd wish I was inside a museum."
At the Inner Harbor, however, some welcomed the warm weather. Andrea Fenwick, who lives three blocks away, relaxed in one of her favorite spots, curled up under some shade from a tree with a good book. Baltimore should be prepared and stay informed as June approaches, Fenwick warned, because "it's only gonna get hotter."
Baltimore Sun Media Group reporter Blair Ames contributed to this article.