Denver is so well located for outdoor activities. It's close to the Rocky Mountains so hiking in the foothills is an activity that can be enjoyed within a few minutes drive.
The day after Christmas, our temperatures were at 60 degrees. The sunshine was warm at mid-day, warm enough to hike up the canyon without a heavy jacket. We did see a few shirtless joggers...but most folks were in vests or lightweight jackets.
Denver day trips like this one are most enjoyable. Waterton Canyon is a scenic hike/bike/jog trail located south of E-470 and Wadsworth. Go toward the Lockheed Martin Astronautics, turning southeast onto Waterton Road.
(OK, my daughter is bundled up more than others because she's been living and teaching in Mexico. To her 60 degrees is chilly!)