The following is from the National Park Service, https://www.nps.gov/mora/planyourvisit/winter.htm
Mount Rainier’s landscape undergoes a dramatic transformation in winter. Its colorful subalpine meadows and lush old growth forests are draped with a thick blanket of snow for much of the year. The sometimes dusty appearing glaciers are freshly covered in white and the snow-covered roofs of the rustic historic buildings are rimmed with icicles, creating a picture perfect setting.
Attractions on the north side of the mountain – Sunrise, the Carbon River entrance and Mowich, for example – are buttoned up for the winter months. Those looking for organized snow play in the park will need to head to head through Elbe and Ashford before passing through the Nisqually Entrance.
Mount Rainier National Park is a popular place to enjoy winter activities. The mountain receives abundant snowfall and the scenery is spectacular. In winter, recreational opportunities are numerous. A winter visit to Mount Rainier can include ranger-guided snowshoe walks, Paradise snowplay, camping, snowboarding and skiing.
Sledding and Sliding: The snowplay area at Paradise is generally open late December through mid-March, depending on snow. Sufficient snowpack is required to protect the meadow vegetation before the snowplay area can be opened. Sledding and sliding are permitted only in the designated snow play area at Paradise. Trees, tree wells, and cliffs make other areas dangerous. For everyone’s safety, use “soft” sliding devices-flexible sleds, inner tubes, and saucers. No hard toboggans or runner sleds.
RANGER-GUIDED SNOWSHOE WALKS
Join a park ranger to learn the art of snowshoeing and discover how plants, animals and people adapt to the challenging winter conditions at Mount Rainier.
Snowshoe walks cover approximately 1.8 miles in 2 hours.
Group size: Snowshoe walks are limited to 25 people, 8 or older, on a first-come, first-served basis. A sign-up sheet is available at the Jackson Visitor Center information desk one hour before each walk. All snowshoe walk participants must be present at sign-up.
Snowshoes – Snowshoes are provided by the park only for those attending the ranger-guided snowshoe walks, and only for the duration of the walk. A $5 donation from each snowshoe walk participant helps the park provide snowshoe walks and repair and replace snowshoes. Additionally, the park concessioner rents snowshoes to anyone wishing to snowshoe in the park; check at the Longmire General Store for availability and rental rates. Or you may use your own snowshoes. Also recommended are a hat, mittens or gloves, boots, sunscreen and sunglasses.
Skiing and Snowboarding – To avoid damaging exposed vegetation, a minimum of 5 feet of snow is strongly advised for skiing and snowboarding. Obtain further information at the Jackson Visitor Center at Paradise (weekends and holidays) and the Longmire Information Center (daily).
In the southwest corner of the park, snowmobiles are permitted for 6.5 miles along the Westside Road from its junction with the main park road as far as Round Pass. Beyond Round Pass, the Westside Road is closed to snowmobile use. Snowmobiles are also permitted on all the road loops of Cougar Rock Campground. The campground is closed to overnight use during winter and the roadway is left unplowed. Contact a park ranger at the Longmire Information Center for maps and additional snowmobile information.
On the north side of the park, no ranger station is open in the winter. The U.S. Forest Service District Office in Enumclaw provides information and maps for White River, Carbon River and Mowich Lake areas. For more information, call the USFS District Office in Enumclaw at 360-825-6585. State Route 410 is closed near its junction with Crystal Mountain Ski Area road, at the north park boundary.
Snowmobiles are permitted on the 12-mile section of unplowed road from the north park boundary on SR 410 to the White River Campground. Snowmobiles may not continue on SR 410 south of the White River Road turnoff. They are also prohibited from proceeding beyond the closure at the White River Campground road junction towards Sunrise. Snowmobiles must stay on the road corridor; they are not allowed to proceed beyond the campground towards Glacier Basin. Be aware of avalanche danger and the weather forecast.
Wilderness permits, required for all backcountry camping, and climbing registration cards are available at the north boundary arch on SR 410 or by self registration at the Ohanapecosh Ranger Station.
Most of Mount Rainier’s roads are closed for winter. The road from Nisqually Entrance to Longmire is open year-round, but may close during extreme weather. The road between Longmire and Paradise closes nightly in winter and reopens in the morning once the road has been plowed. Icy or snowy roads, poor visibility due to weather, and the chance of wildlife along roads can make winter travel challenging. Learn more about how to travel to Mount Rainier during winter.
Dress warmly and stay dry
Cold temperatures, wet snow, and wind can easily rob you of body heat. To avoid hypothermia and frostbite, dress warmly and stay dry. Wear layers of wool or synthetics like pile and polypropylene under a waterproof shell. Avoid exposure to wind. Snack frequently, drink lots of water, and take warm-up breaks indoors.
PAY ATTENTION TO THE WEATHER
It’s easy to get lost or fall when the weather turns bad. The trail can quickly cover with snow, or thick fog can blanket your route. You need to know where you are and how to get to safety. You also need to know how to assess avalanche hazards to minimize potential risk.
When hiking, climbing, skiing, or snowboarding all are encouraged to have the Winter 10 Essentials and know how to use them. In addition, obtain compass bearings to Camp Muir or other off-trail destinations; carry an altimeter; wear rain- and wind-resistant clothing; and take a whistle, a “space blanket” and a snow shovel.
The snows of winter concentrate wildlife where life is easier – where shallow snow provides easier travel and access to food. Parking areas and roadways are efficient travel corridors for deer and foxes, and deer may find the most available forage along roadways.
Many visitors feed wildlife to get a better photograph and some mistakenly think that it helps the animals through the winter months. But this brings wildlife closer to vehicles and people, often with dire consequences. Animals attracted to these busy areas are often injured or killed by vehicles. The feeding of wildlife, an especially significant problem at Paradise, poses a threat to wildlife by increasing the risk of disease transmission (among themselves and to you), unnaturally increasing populations which may prey on other species (jays feed on eggs and nestlings of other songbirds), and causing digestive problems (their systems are adapted for natural foods, not cheese crackers).