The heat index could top 100 degrees for the first time in 2013 this week after a relatively mild start to summer.
Through Sunday, there had been just a single day above 90 degrees in Baltimore this month, on June 1. That tally is likely to grow by four or more over the next week, but is still likely to be at its smallest since June 2009 when not a single day topped 90 degrees.
Monday added one more, when the mercury showed 92 degrees about 3 p.m. at Baltimore-Washington International Thurgood Marshall Airport. That matched the highest temperatured recorded at the airport so far this year, last reached May 30.
The heat was fueling possible storms, with a severe thunderstorm watch issued across Central Maryland on Monday afternoon.
Highs are expected in the mid-90s for a four-day stretch starting Monday, according to the latest National Weather Service forecast. With the humidity, the heat index could near or top 100 degrees Tuesday and Wednesday afternoons.
At least one of those days is expected to set a new bar for the year's hottest temperature in Baltimore.
Temperatures surged to 86 degrees at BWI by 11 a.m. Monday, hotter than most daytime high temperatures over the past week. With dew points in the upper 60s, the air feels wet and soupy.
That was spawning scattered storms across the mid-Atlantic Monday afternoon. Severe thunderstorm warnings were briefly issued in Allegany County about 1:45 p.m., cautioning of large hail and 60 mph wind gusts.
A severe thunderstorm watch, which indicates that conditions are favorable for storm development, was in effect for the Baltimore and Washington, D.C., areas and Southern Maryland until 10 p.m. Some storms could reach the Baltimore area during the evening rush, about 4-6 p.m.
Temperatures typically have to be at or near 100 degrees, with heat index values well into the 100s, for the city and county to open cooling centers.