Crowds that have gathered daily and nightly outside the immigration facility in Oregon's largest city in recent days have embraced the absurd, donning inflatable frog, unicorn, axolotl and banana costumes as they face off with federal law enforcement who often deploy tear gas and pepper balls.
The bike ride is an annual tradition that usually happens in the summer, but organisers of this weekend's hastily called event said another nude ride was necessary to speak out against President Donald Trump's attempts to mobilise the National Guard to quell protests.
Rider Janene King called the nude ride a "quintessentially Portland way to protest".
The 51-year-old was naked except for wool socks, a wig and a hat. She sipped hot tea and said she was unbothered by the rain and chilly 12C temperature.
"We definitely do not want troops coming into our city," King said.
Bike riders made their way through the streets and to the city's US Immigration and Customs Enforcement building. Authorities there ordered people to stay out of the street and protest only on footpaths or risk being arrested.
The city is awaiting the ruling of an appeals court panel on whether Trump can send out the federalised troops after a federal judge on October 5 ordered a temporary hold on deployment.
"Joy is a form of protest. Being together with mutual respect and kindness is a form of protest," the ride's organisers said on Instagram.
"It's your choice how much or little you wear."
Fewer people were fully naked than usual - likely because of the cool, wet weather - but some still bared it all and rode wearing only bike helmets.
