Here's a long snowshoe in winter - 7 miles round trip and 800 feet elevation gain. The lookout is rented in the winter, so be sure no one is there if you climb up the stairs to take advantage of the additional height. 

Find the Skyline Sno-Park off NF-42 about 11.5 miles east of Government Camp on Highway 26. Note that this is NOT at the Clear Lake Campground. Park and climb the snow berm or take the snowmobile route to continue on NF-42 south for 1.5 miles (do not take the right turn after 0.8 miles). There will be a right turn and a gate with signs in winter that it is 2.0 miles to the Lookout. Continue up this road - it's actually paved under all the snow - for 2.0 miles to the lookout. A GPS may give you comfort that you are headed the right direction. There are few skiers or snowshoers here but many friendly snowmobilers. There have been few 2m FM QSOs made from Clear Lake Butte so plan on using HF to get your contacts. And check out the summer trip report to Clear Lake Butte here.