The hot and humid air that settled over Baltimore today should leave the area after delivering no more than two mid-August days in mid-September, forecasters said.
The heat, expected to approach the mid-90s both days, is to taper off Wednesday. A cold front from the Midwest will bring more autumn-like highs of 75 degrees Thursday and Friday, the National Weather Service says.
Autumn itself arrives officially next Monday, Sept. 23, at 7:48 a.m.
Forecaster Bill Miller said today that the hot and muggy conditions are the result of a mass of heat and humidity from the South.
The transition day between summer and fall temperatures will be Wednesday, with highs in the mid-80s, Miller said.
Miller said it's not unusual for hot weather to pop up around Baltimore in mid-September. The daily records slip from near 100 degrees in the first days of September to the low 90s at month's end.
The records for this date were set 21 years ago, when it reached 95 degrees in the city and 97 at Baltimore-Washington International Airport.
Miller doubted the records would be broken today. It was 83 degrees downtown at midmorning.
As the days get shorter, Miller said, the overnight lows for the rest of the week may feel a bit chilly.
He forecast a low of 58 degrees for Friday, which should make for comfortable sleeping. Record lows for mid-September are in the 40s.
As for rain, Miller is calling for a chance of showers by midweek, but he said it is unlikely the rainfall would relieve the region's persistent dry weather.
There was no reported rain yesterday, and the accumulation so far this month has been slightly more than a half-inch at Baltimore-Washington International Airport. The normal amount for September is 3.46 inches.
Based on a normal annual average yearly rainfall of 41.84 inches, 1991 could be one of the metropolitan area's driest.