A tornado warning was issued in northeastern Baltimore County and western Harford County, and large hail and wind gusts approaching 60 mph have been reported as severe storms cross the Baltimore area Tuesday evening.
The tornado warning was issued for areas including Glen Arm, Kingsville, Fork and Joppatowne but was canceled shortly after 6 p.m.
The storms come amid the most intense heat and humidity of the year. Baltimore-Washington International Thurgood Marshall Airport matched its highest reading of the year, 94 degrees, and with the humidity, it felt as hot as 102 degrees, according to the National Weather Service.
The Inner Harbor reached 97 degrees with a heat index of 103 degrees.
A severe thunderstorm watch is in effect until 11 p.m., with threats of damaging winds, intense lightning and large hail. Golf ball-sized and quarter-sized hail were reported around Cockeysville, Owings Mills and Hunt Valley, and a 58 mph wind gust was reported near Hickory in Harford County.
A storm crossing Garrett County around 4 p.m. prompted a tornado warning there.
All of Maryland was forecast to face an "enhanced" threat of severe weather Tuesday, according to the weather service's Storm Prediction Center. The center predicted 30 percent chances of damaging wind gusts and 15 percent chances of severe hail across Maryland.
Temperatures dropped to only 74 degrees overnight at BWI, the region's point of record. That is about 10 degrees above normal lows.
A heat advisory is in effect for southern Harford, Baltimore and Howard counties, Baltimore City and Anne Arundel County from 1 p.m. to 7 p.m.
Baltimore Health Commissioner Dr. Leana Wen issued the first "Code Red" heat advisory of the summer. The declaration opens 11 cooling centers at community and senior centers. Harford County officials urged residents in need of shelter from the heat to visit the county's public libraries.
Baltimore Gas and Electric Co. asked customers to cut back energy usage between 1 p.m. and 7 p.m. in exchange for a credit on their next bill, its first "energy savings day" of the summer. The utility said it doesn't expect demand for power will outstrip supply amid Tuesday's heat.
The temperatures had been expected to be the hottest in at least a year. Last summer's hottest temperature at BWI was 96 degrees on June 18. The airport last hit 97 degrees July 18, 2013.
So far this year, June 12 was Baltimore's hottest day, with a high of 94 degrees.
Temperatures would have had to surpass 97 degrees at BWI to break a record for Tuesday's date that was most recently set in 2010.
The heat wave is expected to be brief. A cold front is forecast to pass through by early Wednesday, dropping highs into the 80s.