Last summer, bicycling devotees Patrick Stephenson and Zachariah Schaap tried to find a way to generate interest in biking among their friends in Minneapolis. They did that -- along with newfound friends in 87 countries, from Australia to Germany, Indonesia to Ireland.

"It just blew up," Stephenson said. "It's crazy."

Called 30 Days of Biking, the rules are simple: For 30 days in a row, people ride their bikes at least once -- it can be around the block or 10 miles to work -- and then tweet and/or blog about the experience. This year's event started April 1, and about 2,000 riders worldwide are participating.

"The Twitter feed is huge," Stephenson said. "We're getting about 100 tweets an hour."

There are riders who brag: "Even though it might snow later in Chicago, and [there's a] 60% chance [of] rain, I'm gonna bike to work today!" Some report their mileage: 'Had a great little 50 km trundle around Tokyo today." While others share the fun they're having: "3 hour ride in gorgeous CA sunshine, I feel normal again."

The chilly weather hasn't stopped local participants.

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Terramoto bike helmet by Giro.

"They take it as a challenge," Stephenson said. "We do have 'lifeline' modeled after 'Who Wants to be a Millionaire?' If you really need to, you can use a stationary bike."

The organizers aren't making any money off this.

"We just want to see people out on their bikes," Stephenson said.

You can check out the website at www.30daysofbiking.com. Or follow the action on Twitter: @30daysofbiking.