After I heard a GA pilot expressing concern about getting into icing conditions, I responded to air traffic control:
Me: “PIREP for the 172 concerned about icing, the freezing level over Santa Cruz summit is 5,000 feet.”
NorCal Approach: “What was the OAT?”
Me: “Well, uh, that would be zero degrees Celsius.”
Bennet Taber San Francisco, CA