Two skiers were killed Saturday in an avalanche near Crested Butte while skiing across a slope of 37°. They were following a summer hiking route.  

I recently found an easy method to immediately assess slope angles while out sking at: http://poleclinometer.com

See image below of the sticker that goes on your ski pole. Must be sized to your pole diameter, but it's inexpensive and easy to use. Note that the angles pictured below are 27°--the upper limit of safe slope angles in avalanche terrain.