Portland, Oregon (CNN) - It's gets pretty chilly this time of year -- especially if you're not wearing pants.
That's the reason behind the 13th annual "no pants subway ride".
This group of transit users in Portland, Oregon stripped down from the waist down to raise attention -- and money -- for local homeless shelters.
The event on the max commuter train isn't isolated to Oregon, either.
It started in New York in 2002.
Organizers say the pantless commuter rides have spread to 60 cities in 25 different countries.