The Darcy family of Fort Washington skated across the ice rink at Dilworth Park on Thursday as "Sleigh Ride" and other festive songs evoking wintry wonderlands played over the speakers.
Erin Darcy, 10, wore a fleece. Older sister Caitlin wore a T-shirt.
Temperatures reached 71 degrees early Thursday, making it the warmest Christmas Eve on record in Philadelphia and nearly the warmest of any day ever in December. The record high for the month is 73, set Dec. 4 and 7, 1998.
Wednesday's high of 70 set the record for Dec. 23, and higher-than-average temperatures are set to continue into the new year.
"It's definitely strange, but it's great," Nancy Darcy, the girls' mother, said.
At the New Jersey Shore, John Hogan, 37, of Cherry Hill, was able to jog on the Boardwalk in Ventnor in nothing but shorts and a light sweatshirt.
"Unbelievable," he said.
Other places in the region - including Allentown, Atlantic City, Trenton, and Wilmington - also set Christmas Eve record highs.
A weather pattern tied to the warming of the Pacific Ocean near the equator brought springlike temperatures to the Northeast, snow across the West, and deadly tornadoes in the South.
Storms from the Gulf Coast to the Northeast caused hundreds of flight delays during one of the busiest travel days of the year. Flights into Philadelphia International Airport were delayed an average of 44 minutes Thursday afternoon because of weather.
This month is on track to be the warmest December on record in Philadelphia, with average temperatures of 50.4 degrees in the last few weeks, according to the National Weather Service. That is nearly 12 degrees above normal.
In Chester County, growers who donate to the county food bank are still pulling broccoli, kale, and other greens from their fields. They will most likely be able to keep picking into January, said Phoebe Kitson-Davis, a manager at the food bank in Uwchlan Township.
"It's terrific," she said.
Fran Convery of Valley Forge was in Philadelphia with his family for a holiday tradition - looking at the decorations and having lunch at the Reading Terminal Market.
He wore red plaid shorts and a red pullover, but he gave a bah-humbug scowl when asked about the weather.
"I'd rather it be cold. I'd rather have snow on Christmas," he said. "This past week and the days leading up to it did not feel like Christmas, with the warm weather.
"But when we start doing this stuff, it does."
At the Shore, the weather was foggy and rainy Thursday, with temperatures in the 50s. If this were a summer vacation, it would be a washout.
But for Hogan, a physician at the Hospital of the University of Pennsylvania, the annual visit to his mother-in-law's home was a balmy treat as he and his 21-month-old twin sons had fun at the playground.
"People say you'll get sick of it," he said, referring to the warmth. "But so far not."
His advice: "Keep getting outside until winter does what it's supposed to do."
Staff writers Amy S. Rosenberg and Julia Terruso contributed to this article, which also contains information from the Associated Press.