The good news: Temperatures tumbled -- 21 degrees in three hours at one monitoring station as a cool front moved in.
"The heat wave is definitely over," said Ross Dickman, National Weather Service meteorologist.
Before the cooling began, however, a high of 94 degrees was recorded shortly after 1 p.m. at Long Island MacArthur Airport in Ronkonkoma -- a record for the date. Three hours later, the temperature had plunged to 73.
Downed trees and branches took out power lines, said Mark Gross, Long Island Power Authority spokesman. At 10 p.m. the utility was reporting 5,400 customers in Nassau and Suffolk counties without power.
"We also took a lot of lightning strikes on our system," Gross said. "We have been monitoring the storm and planned accordingly, bringing in extra crews" to deal with anticipated problems.
In Garden City, traffic signals were still out at 7 p.m., prompting police to direct traffic at a number of intersections.
The LIRR experienced delays on all 10 of its Long Island branches "due to weather-related signal problems." As of 8:15 p.m., trains leaving Penn Station were running on or close to schedule.
Nassau County fire departments were "inundated" Friday with calls related to downed wires and automatic alarms going off.
The outlook for the first official weekend of summer, though, is good. Mostly sunny days are forecast, with highs in the low 80s, meteorologist Ashley Sears said. "People can actually go out and enjoy it," she said.With Gary Dymski