SAN DIEGO (FOX 5/KUSI) -- Need to work off that turkey? The County of San Diego Parks and Recreation is celebrating a holiday they came up with known as "Green Friday." Green Friday, which occurs on Black Friday, celebrates outdoor experiences with free family-friendly activities in parks and preserves across the region. All of the parks that charge $3 for park day use will be waived on Green Friday, according to the county. There are ranger-lead activities such as planned rides and hikes, while volunteer opportunities include tree planting and habitat restoration. "Events are active and educational – aligning with our mission to balance recreation with efforts to protect and preserve land and local environment," County Parks said. BOOT CAMP WITH MISSION: FIT 9 – 10 a.m. on Friday Pioneer Park, 1521 Washington St., San Diego, CA 92103 Work out with certified trainers with Mission: Fit in a city park. Register at 619-301-3505 or [email protected]. ACORNS 101 10 – 11:30 a.m. on Friday Ramona Grasslands County Preserve, 760-788-3326 Learn about different types of trees and acorns, and how to pick the good ones. For more information on other events on Green Friday and throughout the weekend, click here.