I'm surprised to learn there are organized day tours to either of these places in December.

In December, Mt. Rainier is likely to be shrouded in clouds so chances are you won't be able to see it if you go there and, in my experience, it isn't possible to "see" Olympic NP on a day trip from Seattle.

Assuming you can book a day tour, wait until the last minute and go to Mt. Rainier if the mountain is visible otherwise go to the Olympic Peninsula or to one of the San Juan Islands.

HTtY

PS San Juan is my favorite San Juan Island, but Orcas is the first choice of many others.

Well, the combination of lousy weather and very short days is going to curtail your options big time.

The entrances to Mount Rainier NP are around two hours drive time from Seattle, but the visitors centers (at least an hour longer) will be very snowbound, and unless your car (rental or borrowed?) has snow tires or chains, there's a good chance you won't be able to get to them. (If memory serves, the Paradise visitors center on Rainier is the snowiest place in the USA.)

The nearest point in Olympic NP to Seattle (either the Hurricane Ridge area on the north end of the Olympic Peninsula or the Quinault rain forest valley in the southwest corner of the park) are around 2 1/2 to 3 hours' travel time (road and/or ferry) from Seattle, so if your time is one day to go there and back, you'll be driving in the dark at least part of the time. And Hurricane Ridge will also likely be snowy, while the rain forest valley will be... well, rainy. But that might be your best shot.

Or else skip the national parks and spend an enjoyable day poking around Puget Sound - a day on Whidbey Island, for example, could include a fun ferry ride, some very cute towns, the spectacular Deception Pass area, and way less time traveling. But that depends on your priorities.

And welcome to Fodor's!

I'd have to know more about the projected itinerary to decide for myself. Olympic is huge with 3 distinct sections (mountains, rain forest and coast) but since it's 3 hours from Seattle, it's hard to imagine an itinerary that does it justice in one day. Maybe they shorten the drive by taking the ferry? Mt. Ranier is 2 hours from Seattle so that helps, but I'm wondering how much of the higher country would be accessible due to winter conditions?

Do you have a link to the tour with an itinerary?

Thanks for the input

Gardyloo, we're looking at tours which include pickup and transport. We considered renting a car, but were discouraged by the thought of chains as you mentioned.

WhereAreWe, link to the tour is: http://evergreenescapes.com/olympic-national-park-tour
Thoughts?

Based on the 2 options presented, I'd go with Olympic. That tour is 11 hours, Mt. Ranier is 10 so I suspect your actual time outside would be approximately the same on both. But you'll have more diversity with an Olympic tour, and I suppose if someone else is driving it's not as bad as going it alone.

But if you have travel companions, I'd rent a car for the day and switch off driving duties. Far cheaper, and then you can decide which park to go to based on current weather. Even then I think Olympic would be better, I'm just picturing snow and cold at Ranier and that doesn't sound like fun. The coast and rain forest at Olympic at least shouldn't be frozen.

Remember to check the roads before you head to Mt. Rainer..they are often closed for the Season. I'd go for the Olympic myself...lots to see and do.

Did anyone happen to see the video of the rescue yesterday from Mt. Rainier? The rescuers took up 2 extra pairs of snow shoes for the guys that spent over 40 hours in a snow cave they built after calling 911 to report their position. They only had crackers and no overnight stuff when a sudden blizzard came up.
You would be much safer in Olympic NP.

I saw that, it even made the national news. Probably lucky they made it alive. You can bet the park service there is being super extra careful after losing two rangers this year(one in a search and rescue and the other female that was shot). So, I would imagine they would be more cautious about putting themselves in jeopardy.