The heat wave that enveloped much of the region in recent days broke with a bang Wednesday afternoon, as a barrage of lightning and heavy rain swept across Massachusetts, flooding roadways, downing trees, and leaving more than 20,000 people without power.
The storms moved across the state quickly and brought much more comfortable weather for the remainder of the week, said Weather Service meteorologist Charlie Foley.
He said sun and low humidity is expected starting Thursday and continuing through Sunday. Daytime temperatures will be in the low 80s, dipping into the 70s Friday.
“The big thing is that this frontal passage will mark the end of the hot and humid air mass that we’ve been experiencing,” Foley said.
State Police said the North Shore experienced roadway flooding Wednesday in several locations, including portions of Route 1 in Peabody, which was under 2 feet of water. The Nahant-Lynn rotary and the Lynnway at Commercial Street also flooded, and the Nahant Causeway had standing water, as did Route 1 southbound at Route 60, State Police said.
‘This . . . will mark the end of the hot and humid air mass that we’ve been experiencing.’
Trees fell on houses and cars in the eastern part of Arlington, police said, and roads were blocked for about two hours in the evening. Arlington police Captain Richard Flynn said most of the affected roads, including parts of Massachusetts Avenue, were open by about 8 p.m.
A tree limb fell across Route 16 in Somerville at around 6:30 p.m., closing several lanes for about 90 minutes, according to State Police.
In Malden, Route 99 was backed up for about a mile at around 3:15 p.m. and a deep puddle nearly 50 yards in width had accumulated in the parking lot of a mobile home park located just off the road.
At one point, National Grid reported about 20,000 customers without power, mostly on the North Shore, but shortly after 11 p.m that number had dropped to about 6,000.
National Grid spokeswoman Charlotte McCormack said extra crews had been brought in before the storm.
NSTAR spokesman Dennis Galvam said about 1,500 customers in Greater Boston had no power at about 11 p.m., and it was not immediately clear when power would return.
Lightning was blamed for fires in at least two areas. A three-story home on Milton Avenue in Dorchester caught fire at about 3:30 p.m. when lightning struck the attic, the Boston Fire Department said.
In Rockland, lightning strikes caused two fires in the afternoon, said a town fire dispatcher.
And the Massachusetts Bay Transportation Authority reported evening weather-
related delays ranging from 10 to 30 minutes on several commuter rail lines, including Needham, Lowell, and Fairmount.
Globe correspondents Melissa Werthmann, Sarah Mattero, and Matt Woolbright and John R. Ellement of the Globe staff contributed to this report.