It is all about the hours of having temps below 25-26 degrees wet bulb. I am borrowing some language from Killington's snow report.

A quick snowmaking lesson:
Ideal snowmaking conditions include outside temperature of 28 degrees with 50% humidity. While 28 degrees with 75% humidity is pretty good and 28 degrees with 100% humidity is marginal for snowmaking.



Ambient temperatures are not what we all look at. It is the wet bulb temperature. The lower the humidity the lower the wet bulb. Right now (11:30am) at the base of LP it is 35 ambient degrees but because the humidity is only 57% the Wetbulb is 30.4 degrees. Still too high for good snowmaking. At Allyn's lodge ambient is 27 degrees, humidity is 77% so wetbulb is 24.9 degrees which is good for snowmaking. The summit is 20 ambient degrees with near 100% humidity so it is 20 wetbulb which is very good for snowmaking. Hope this helps all understand some of the facts behind where and when snow can be made.