Conversely, the probability of it being < 32-F on the equator (at or near sea level) on Dec 1 approaches 0%, as well.
Another way to phrase what I'm looking for: On what date in the calendar year does the probability of the air temperature being above (or below) X approach 0% for a given location/city?
So, say, for Washington, D.C.-- after (or before) what date in the year is it virtually impossible for the temperature to be above, say... 80-F?