Sitting on the sidelines while his pals ran the Santa Speedo Run the last four years, Mike Hagopian was intrigued by the idea of stripping down to his skivvies and sprinting through the streets of Downtown Boston in 30-degree temperatures.

“I had mixed emotions,” said the 29-year-old North End resident who is running for the first time Saturday. “I thought it would be pretty fun, but as they went out to go run I was still sitting with my drink."

The 500-person run, which recently incorporated as a nonprofit called SSRuners, began 11 years ago after Jon Ianelli hatched the idea while drinking with his buddies at a bar.

“We did it as a joke the first time,” Ianelli, 37, said. “We grabbed a boom box playing the Muppets Christmas Carols and started to run. People went nuts for it.

“I thought, ‘Maybe I can do some good for charity.’ It snowballed from there.”

The run has raised $640,000 for various charities over the last decade and hopes to take in another $200,000 this year for Hospitality Homes, Play Ball! Foundation and Starlight Children’s Foundation.

Saturday’s forecast calls for highs in the upper 40s and sunshine. But Hagopian knows his first run could be “pretty painful” if lows dip into the 30s.

Latest From ...