See details from their announcement.

Take the Winter Warrior Challenge and make a healthy, environmental choice to bike through the winter.

Biking to work or class during the winter months may seem like a chilly challenge, but it actually isn't that hard, and turns out to be pretty fun! Join the Winter Warrior Challenge and bike to work or class as many times a week as you can from November 30- December 12, as long as you feel safe and comfortable. The Winter Warrior Challenge is intended to encourage winter biking as a healthy, fun and environmentally-sound way to commute to work or class. Bundle up, winterize your bike, and register today!

Here are the rules:

1. Ride your bike as much as you can...except when:

It's so icy that you'll probably skid out and hurt yourself. Be safe and don't bike until the streets are clear.
It's total white-out conditions.
You're so sick you can't do anything but sleep all day and drink hot cocoa.

2. Submit your trips and miles each week on Mondays, Dec. 7 and 14 for a chance to win weekly prizes from a random drawing. At the end of the challenge, prizes will be awarded for the most trips number of trips and most miles.  Top prizes for most trips include a Fat Bike rental for one weekend from World of Bikes, a jersey from the Iowa City Bike Library, and other prizes TBA. So whether you bike 1 mile five times a week or 5 miles once a week, you can still win a prize.

3. Take pictures of your winter biking fun and submit them here or use the hashtag #hawkwinterwarrior on Facebook, Twitter or Instagram. Three winners chosen by an esteemed panel of judges from the UI Bike Advisory Committee will receive a $10 gift card to Active Endeavors. 

It's pretty simple. We won't complicate this with a point system like our other challenges. We figure it's hard enough to bundle up and brave the elements, so we're rewarding you just for getting out there and being a Winter Warrior!