Best national park or wilderness area to visit in December?

Hawaii Volcanoes National Park. Great weather, though a bit rainy on the Hilo side, but you definitely won't have to wear tights. Can check out the rest of the Big Island outside of just the park. You won't be disappointed, check out alaska air flights from Seattle.

The Muir Woods area north of the Golden Gate Bridge has some trails leading down to Stinson Beach and from Fisherman's Wharf, San Francisco to Presidio, and then across the Golden Gate Bridge to Hawk Hill. I think you can continue on to Stinson Beach from there, but I'm not sure.

In Auburn, CA, east of Sacramento, you can hike/run the lower section of the Western States 100 trail. Whether you'll have to wear tights depends on the weather in December. The run from Auburn down to Sacramento is also nice. Sacramento is only three hours from SF, so you could do them both on your trip.

If you really want to get away from it all, consider Big Bend National Park in west Texas. It's a desert with a river running along one border. If you're lucky, you can overnight in Marfa, TX and see the Marfa lights, one of the most frequently occurring unexplained phenomena in the USA. The wildflowers don't bloom until late January.

I found the Grand Canyon to be a nice place to visit for a few hours in the morning and late afternoon to see how the shadows play over the canyons. Don't get me wrong, it's awesome, but it's not a place I'd want to trail run. Lots of people do though. Whatever...

As others have suggested keep heading south or you could find the majority of your time spent negotiating snowy roads.

There is a great loop any time of year but especially in the winter without crowds. From the north Zion through Vegas, Hoover Dam, South Rim of the Grand Canyon, through Monument Valley (see if you can get a lottery to the Wave on the way there), Moab (Arches), Bryce. There are many other great places along the way to/from such as Yosemite, Ansell Adams Wilderness, Kings Canyon, etc. although they will not be warmish as you suggest. The way back north Mesa Verde, Million Dollar Highway, Rocky Mountain National, Grand Tetons, Yellowstone, Glacier although those listed for the trip back north will bring greater snow risks of huge snow totals.

Sounds like a great opportunity. Enjoy!

There are also many other spots to see

fisky wrote:

I found the Grand Canyon to be a nice place to visit for a few hours in the morning and late afternoon to see how the shadows play over the canyons. Don't get me wrong, it's awesome, but it's not a place I'd want to trail run. Lots of people do though. Whatever...

Dude, the only reason to visit the Grand Canyon is to hike down to the bottom. If all you do is stay at the top you should save your time and money. Not sure what it's like in December, but I hiked it in March and had a great time. There was snow on the ground at the top, but we were sweating pretty good by the time we got to the bottom. I would guess it was 75 degrees or so down there. I don't know if you can really RUN the whole thing, but it makes for a great 1-3 day hike.

Death Valley National Park, mostly in California but no more than about three hours from Las Vegas. Altitudes ranging from 282 feet below sea level to 11,049 feet above sea level, so you can choose your weather. It's huge, with countless places to hike, places to go and things to see, though only a few places have trails. Lots of dirt roads, though. The downsides are the great distances involved because it is so big and so remote, a shortage of lodging and fuel options, and the fact that it gets dark so early (sunset about 4:30) there in December. Nights are long if you are camping, and it can be near or even a little below freezing overnight there even at the lowest elevations. Daytime highs in the 60s and 70s in much of the park with not much chance of rain. The stargazing is spectacular, if that interests you. Just be sure you're pretty self contained because most of the park is a long way from any help and a long way from any towns.

Crater Lake National Park, Southern Oregon