Geno Carapico watched from his upstairs window in the 3400 block of Chestnut as a falling tree shattered the windshield of a Ford Focus near the front of his house. The tree also damaged a nearby minivan.
"It went pop, pop, pop, pop when the roots snapped, and when they snapped, it came down quick," he said.
Sherry Campbell, who lives two blocks away, surveyed the damage with some relief. "I had just moved my car five minutes before. Otherwise it would have fallen on mine," she said.
Lightning and wind gusts caused widespread problems across the region. Anne Arundel County emergency operators alone fielded 70 calls for assistance with fires, downed trees and wires, and darkened traffic signals. Most were cleared quickly.
A 26-year-old resident of Queenstown Road in Glen Burnie was treated for smoke inhalation. He tried to rescue pets from his house after lightning ignited a fire in his dryer vent. The blaze was under control within an hour, officials said.
Lightning struck the chimney of a house on Blenheim Farm Lane in Phoenix, Baltimore County, then ignited a fire in the basement. No one was injured.
The owner, retired Johns Hopkins Hospital physician Patrick Murphy, said he heard a loud boom and watched his computer screen go black. Then a repairman working at the house reported smoke pouring from a basement utility room door.
Inside, he found a water heater, a wooden joist and the insulation covering a natural gas pipe burning. The repairman used an extinguisher to snuff out the burning insulation, while firefighters who arrived shortly afterward put out the fire in the joist.
"Fortunately, the gas line didn't catch fire," Murphy said.
Lightning also fried a computer at Bennigan's Restaurant at the Centre at Golden Ring on Baltimore County's east side. About 20 patrons and employees were evacuated as smoke wafted from the electronics.
Fallen trees caused 30- to 40-minute delays on the light rail line between BWI Marshall Airport and Linthicum.
Yesterday's storm popped up southwest of Baltimore as temperatures reached 96 degrees at BWI, and 98 degrees downtown.
At 1:25 p.m., with thunder already pealing across the city, the National Weather Service issued a severe thunderstorm warning for Anne Arundel County. The warning was later expanded to include the city and Baltimore County.
Although the forecast had mentioned a "slight," 20 percent chance of a thunderstorm yesterday, no other watch or warning was issued before the storm developed.
Zubrick said the storms formed along what meteorologists call the "bay breeze front." That's a region along the entire western shore of the Chesapeake where hot air rising off the land draws in cooler, wetter air from the bay.
Where the two air masses collide, the combined heat and humidity can fuel thunderstorm formation. "They form in place," Zubrick said. "It wasn't like it was moving across Western Maryland," where it could be spotted and tracked for hours. Sometimes they form in as little as 30 minutes.
"It's really beyond the level of science to predict there will be a storm in Cockeysville and not one in Baltimore City, and another in Columbia," Zubrick said.
Before the storm ended, more than 1.8 inches of rain had fallen at BWI. Temperatures there fell from 96 to 75 degrees before the rain let up, but they quickly rebounded well into the 80s.
Quarter-sized hail was reported in the city's Druid Hill Park and in Linthicum Heights, Anne Arundel County. Trees were toppled in Cockeysville, Jarrettsville and Washington, according to the weather service.
The Baltimore Health Department continued its Code Red Heat Alert, re-opening cooling shelters across the city.
The heat index at The Sun reached 109 degrees at 1:30 p.m. as the temperature reached 94 degrees and the humidity climbed well above Monday's level.
Sun reporters Gadi Dechter, Nicole Fuller, Richard Irwin, Brent Jones, Julie Scharper, Andrea Seigel and Julie Turkewitz contributed to this article.