Mt Rainier is ranked as one of the worlds deadliest volcanoes and here's why you might still go play on its slopes.
Luckily for us the volcano is currently classified dormant with the most recent significant activity happening in the 1800's. Let's be honest though, that's not that long ago... If it were to blow again it would be massively devastating for the residential areas surrounding it. It's effect would be seen and felt by most of the west coast hence its deadly classification. On a clear day you can see Mt Rainier for hundreds of miles in every direction, and the entire area surrounding the mountain creates one of Washington's most exciting areas to explore, the Mt Rainier National Park.
You'll find alpine meadows, peaks, 25 glaciers, waterfalls, and over 91,000 acres of old-growth forest with plenty of climbing, hiking, and camping options all of which require some type of fee or permit. As a little hack we'd recommend looking into the America the Beautiful Pass that will give you annual access to over 2,000 of America's National and Federal Lands and Parks and can be used for several of Washington's best outdoor recreation areas.
For the experienced mountaineer this mountain/volcano presents the state's tallest summit rising to 14,411 feet! That makes it the 4th tallest summit in the USA mainland. The summit is made by thousands of mountaineers each year and attempted by even more. Despite the popularity, this is a VERY dangerous activity and requires gear and training that makes hiring a guide a good idea if you're unfamiliar with expeditions of this nature. For most of us however we are happy enough to play in the park at some of its lower altitudes.
For those with kids, dogs, or bad knees there are 4 managed campsites in the park with a combined 486 campsites making car camping a very enjoyable way to explore the park. Most of the sites are found in 3 of the 4 camping areas. If you need help deciding which would be right for you then check out the camp capacity's, fees, and locations here.
For backpackers you'll need permits for any overnight camping but there are also hundreds, if not thousands, of areas to camp alongside the trails as you wander this epic backcountry. The glaciers, valleys, and changing altitudes as you hike alongside this massive mountain really do offer some of Washington's best backcountry views that will offer memories you won't soon forget.
This park has one of the most concentrated number of hiking trails in the state. There are literally hundreds to choose from! Loops, day hikes, out and back trails, peaks to reach, etc. I we had to suggest just one it would without a doubt be the Wonderland Trail. This trail really shows off the diverse landscapes of the mountain as it snakes through peaks, alongside rivers, and takes you to alpine lakes while you walk north/south alongside the west side of Mt Rainier. To help find the best trail for you and your would be adventure I'd visit WTA's Hike Finder tool. WTA will have details and typically decent trail conditions on most, if not all, of these hikes. They really are the states authority when it comes to hiking trails.
This area is a popular place to get outside and use all your winter toys too. As the park receives plenty of snow in the winter you'll find all sorts of winter activities like sledding for the kids, snowshoeing, snowboarding/skiing, and snowmobiling. They even have ranger guided snowshoe hikes for those who'd rather have a little guidance to the area. For more info on getting prepared for these activities there is a ton of helpful information on the parks website.