Cairn Hill located less than three miles west of Blewett Pass is one of a couple scenic summits on the western ridge. The summit earned its name due to a large cairn located on the summit. Because of the lower elevation in comparison to nearby Diamond Head or even the Teanaway, and the lack of elevation gain from Blewett Pass it not as desirable as many other peaks in the area. Because the summit is located on the Leeward side of the Cascade it is home to dramatically dryer weather than that on the western side. You have a dramatically better chance of running into sunshine on this side of the mountains that on the western side. This though also makes for MUCH hotter summers and colder winters. If it is a hot day in Washington avoid this summit!
Cairn Hill is a smaller summit in this general area. However on the way up during a snowshoe views west towards the Enchantments and the Teanaway from the road are excellent and the views from the summit looking east towards Diamond Head and other summits to the east are well worthwhile. On the summit the views focus specifically to the north, east, and the south. Neighboring Old Pass Hill roughly two more miles to the east will have the better views towards the Enchantments.
In summer this is just another smaller summit in the Eastern Cascades with good views of the sorrounding area. All it would require is just a quick walking bushwhack from the nearby forest road below. For easiest bushwhack route to the summit follow the northwestern ridge all of the way to the summit. Though this summit might be interesting for some peakbaggers over the summer, I would not recommend it for that time unless the weather is really bad everywhere else.
I highly recommend you hike to this summit in either fall when some of the western larches on Diamond Head across Blewett Pass are out, or winter when this hike become a 5 mile, 850 foot roundtrip snowshoe up to the summit. Though parking does require a Sno-Park pass these summit are well worthhile provided you stay mostly on the road. Provided you stay on the basic path to the summit this mountain is a relativly safer mountain to do in moderate to considerable avalanche conditions (2 or 3 according to the Northwest Avalanche Center). Obviously no mountain is ever 100% safe so use caution especially in high avalanche danger. Also so I don't lead any into a false sense of security never go hiking here or anywhere else in extreme avalanche conditions (5) and pick even lower elevation, if possible with low or no snow on the summit during high avalanche (4) forecast. If your group is in decent shape combined Old Pass Hill with Cairn Hill for a 9 mile, 1800 foot snowshoe. Both these peaks have distinct views and are well worthwhile in winter.
VIA BLEWETT PASS IN WINTER: Take 97 to Blewett Pass. Blewett Pass will be well marked on the western side of the road. On both sides of the road will be Sno-Park signs and there will a fair amount of snowmobile traffic in the area. Be respectful of where to park because the snowmobile truck will need space to park there vehicles in and out of the parking area.
VIA BLEWETT PASS IN SUMMER: Take 97 to Blewett Pass. Turn west onto Forest Road 7324. At 0.4 miles make a left onto Road 500. NOTE: Road might be in poor condition or not even open in early summer. Take two miles until you are on the western ridge of Cairn Hill. Pull off in good area off the road.
Red TapeIn winter a SnoPark Pass is required ($21 for the day and $42 for the week).
CampingThere are areas in which you can do some backcountry camping in the area such as Haney Meadows. As for summit area I would discourage camping on the summit due to its close proximity to Highway 97.
Trip Report LinksGeneral information on Cairn Hill
A brief trip report on Cairn Hill and neighboring Old Pass Hill"
Another good trip report with Cairn Hill and Old Pass Hill
Blewett Pass LinksLink to live camera of Blewett Pass
Information on winter trail in Blewett Pass. Though much of the information is for snowmobilers, there is plenty of information for hikers.
Snow information at Blewett Pass from the Snotel located at Blewett Pass. This will give you an idea about how much snow is at the pass and what to expect.