Unable to see the top of Pike's Peak (it was snowed in) we headed for Estes Park CO and Rocky Mountain NP. Of course, the snow that closed Pike's Peak also affected RMNP. At Rainbow Curve, 20 miles into RMNP, Trail Ridge Road was barred to traffic because of snow and ice.
The overlook at Rainbow Curve was open and we drove there to see what an early Colorado winter looks like. At 1.30 in the afternoon it looks like this. The mountains are still magnificent, but at 11,000 ft it can get pretty nippy.
At 11,000 ft, we're about 500 ft below treeline. 'Treeline' is the altitude above which trees just won't grow. It varies with latitude; in Colorado, treeline is about 11,500 ft. A Ranger told me that treeline is dependent on the local weather: if the average temperature in the warmest month of the year is above 50°F, trees will grow; below 50°F... no trees.