Although the recent cold snap would argue for an earlier date, the official start of winter is Dec. 21. It's the shortest day of the year, when the sun is farthest south in the sky at noon.

At Tilden Regional Park in the Berkeley hills, naturalist "Trail Gail" Broesder will mark the occasion by leading a hike to the top of Wildcat Peak to view the sunrise. The hike leaves at 6:15 a.m. Dec. 21 from Tilden's Environmental Education Center. It's for ages 12 and older. Bring your own hot beverage and share stories of solstice traditions.

I've hiked to that ridge top myself at sunrise, and if it's a clear day, the views are truly spectacular. The rising sun casts a golden glow over San Francisco Bay, the city, the Golden Gate and Mount Tamalpais. And the time I was there, a coyote chorus saluted the dawn. If you prefer something more sedentary at a later hour, join interpretive student aide Morgan Rani Evans from 2 to 3 p.m. Dec. 22, by the center's fireside for a cup of hot cocoa, holiday stories and nature lore. Bring your own marshmallows.

The programs are free. The center is at the north end of Tilden's Central Park Drive. But because of construction, you have to park at the end of Lone Oak Road off Central Park Drive and follow the directional signs. If you're coming for the hike, bring a flashlight. It's dark at 6 a.m. For details, call 510-544-2233.

Leona Canyon: Oakland's Leona Canyon is the destination for a naturalist-led stroll from 10 a.m. to noon Dec. 22. It's a moderate 3-mile hike to the ridge and back.

Meet at the staging area on Canyon Oaks Drive off Keller Avenue just east of Interstate 580. A word of advice: There are no toilets in the park. For details, call 510-544-3187.

crabby open house: All sorts of special activities are planned during a holiday open house from 10 a.m. to 3:30 p.m. Dec. 26-27 at Crab Cove Visitor Center on Crown Beach in Alameda. The center will also offer its usual programs Dec. 28-29.

The open house will feature nature crafts, games and other family-friendly activities. Nature videos are scheduled from 10:30 a.m. to 12:30 p.m., with popcorn and cider served. Bird bingo (bird-watching) with prizes is from 1 to 2 p.m., low-tide exploration is from 2 to 3 p.m. (wear mud boots) and fish feeding is from 3 to 3:30 p.m. Crab Cove is at 1252 McKay Ave. off Central Avenue in Alameda. For details, call 510-544-3187.

FLOWER TIME: 'Tis the season now when manzanita starts to flower in white and pink and toyon displays red berries. At Black Diamond Mines Regional Preserve in Antioch, naturalist Bob Kanagaki will lead a hillside hike in search of these beauties from 10 to 11:30 a.m. Dec. 21.

It's for ages 7 and older. Meet Bob at the parking lot at the end of Somersville Road, 5 miles south of Highway 4. The hike is free. Black Diamond Mines charges a $5 parking fee per vehicle when the kiosk is attended, and rain would cancel the hike.

Next door at Contra Loma Regional Park, naturalist Eddie Willis will lead an easy walk around the park's reservoir from 9 to 11:30 a.m. Dec. 22, to view some of the wildlife. Meet Eddie near the boat launch ramp just past the entrance kiosk. Contra Loma is on Fredrickson Lane off Golf Course Road in Antioch. There's a parking fee of $5 per vehicle. For details on either hike, call 888-327-2757, ext. 2750.

Big Break regional: Naturalists at Big Break Regional Shoreline in Oakley will celebrate the winter solstice with a campfire program from 3 to 6 p.m. Dec. 22, including games and other activities. The event is free. Big Break is on Big Break Road off Main Street in Oakley. For details, call 888-327-2757, ext. 3050.

Ned MacKay writes a regular column about East Bay Regional Park District sites and activities. Email him at nedmackay@comcast.net.