For the first front of cool continental air to arrive.
|Chart showing the frequency distribution|
of when the first "official" cold front arrives
in Naples FL, by decade
The problem as of late:
Starting in the 2010s, the arrival of the first official cold front has slipped from October to November. Or in other words, it's happening later than normal. The good news is a front of cooler air is finally on its way. The bad news is that it will not count as an "official" front.
For that to happen, nighttime temperatures have to drop into the 50s for two consecutive nights.