Posted today. The intro:

December is a gift to hikers drawn to Mount Diablo, the peak dominating the East Bay landscape.

It’s a month when occasional rains wash smog from the sky and open amazing vistas (you’ll see snowcapped Sierra peaks on the best days). A hint of green returns to the state park’s hillsides, but the thirsty ground absorbs most of the moisture, so the trails lack the ankle-deep muck of the later rainy season.

The Diablo summit area has great views, easy trails and a nice museum. It’s a natural starting point, but there’s a lot more park beyond the peak. Trails twist through rich oak woodlands and rocky canyons. The Rock City area has some of the most curious sandstone formations in the Bay Area (copiously decorated by industrious delinquents, alas).

Being a mountain, Diablo practically begs you to climb it, floor to ceiling, from near sea level to its 3,849-foot peak. Do it if you must, just be mindful of the mountain you’re missing on the way to that tiny bit at the top.

Read the whole thing for trail recommendation.