But people heading for the San Francisco Bay were freezing for a reason. They were trying to raise money for the Northern California Special Olympics.
Hundreds of costumed and plain-clothed participants and teams jumped into Aquatic Park followed by a dip in the bay on Saturday.
And it worked- so far the "Special Olympics Polar Plunge" has raised $250,000.
The water temperature was about 50 degrees.
ABC News contributed to this story.
