Tuesday was Baltimore's sixth 90-degree day this month, and at least one more day of summer heat is forecast before slightly cooler and much drier air arrives for the weekend.
Baltimore-Washington International Thurgood Marshall Airport reached 93 degrees at 2:16 p.m., while temperatures peaked at the Inner Harbor at 92 degrees at 12:43 p.m.
The heat index hovered in the lower- to mid-90s around the region, with moderate to high humidity.
The heat prompted Baltimore County schools to close two hours early.
Two areas of high pressure, one lower in the atmosphere over southwestern Virginia and another about 30,000 feet high over West Virginia, were keeping skies sunny and causing hot, dry air to sink over the region, said Kevin Witt, a meteorologist with the National Weather Service's Baltimore/Washington forecast office.
Each day of September has hit the 90-degree mark at BWI except for Saturday and Sunday.
There have already been more 90-degree days in September than the four posted at the airport in August, and as many as were recorded in June. With Wednesday also forecast to reach the lower 90s around the region, we are likely to match July's tally of seven 90-degree days.
Relief is forecast Thursday as a slow-moving cold front crosses the region, likely producing some thunderstorms.
After that, highs are still forecast in the 80s Friday into the weekend, but with lower humidity. Normal highs this time of year are in the lower 80s.
By early next week, highs are forecast to drop below normal, reaching only the mid-70s, perhaps, Witt said.