I want to revive an old
  topic, but I thought I'd start a new thread since it's a new frost
  season and the code may have changed since the original topic.
 
I would like to request (1) the Sky threshold be changed to a lower
  number (currently 70% per the last conversation) and (2) add a PoP
  threshold. The Sky threshold just seems way too high to me, and while
  I don't have hard evidence, we typically see early/late season frost
  on cool, clear, and calm nights. If sky cover is over even 40% I can't
  see us getting widespread frost. So, I think the number should be
  lowered to at least 50% from the current 70%. Second, having both
  frost and precipitation in the same period sounds silly. While it's
  possible in a 6-hour time frame (rain ending then skies clearing out
  and temps crashing), in most cases where frost will be mentioned, it
  again needs to be a cool, clear, and calm night. While yes, precip
  chances are probabilities, and if we have a 15% chance of rain it
  means there's an 85% chance it won't rain, it still sounds silly to
  mention frost and precip for the same timeframe.
I've attached some screenshots all valid for the same time period
  that shows an example of frost being included when we have cloudy
  skies and precip chances.