Astronomically speaking, autumn began at 2:50 AM EDT Saturday September 23rd. Across West Central and Southwest Florida, however, the temperatures are likely to be anything but fall-like. Usually high humidity with dew points in the middle 60's to middle 70's, along with high temperatures in the mid 80's to lower 90's persist well into October.
The first shot of cooler drier air is usually rather short lived - lasting only a day or two. The real cool down doesn't usually occur until November. A good way to examine the timing of the first cool down is by looking at overnight low temperatures which are highly dependent on a few factors, not the least being the amount of moisture in the air near the ground, along with the amount of cloud cover and winds. The amount of moisture is determined by looking at the dew point. In general, overnight low temperatures cannot fall below the dew point. Therefore, if the dew points are still in the middle 60's to middle 70's, then the overnight low temperatures are also likely to be in the mid 60's to mid 70's unless a cool front moves through during the night. To see when the first cool front typically moves across the region, the long-term mean dates of specific low temperature thresholds since consistent records beganare listed below.
Examining the tables and maps below, the long-term mean date of the first shot of cooler drier air appears to be during mid-October. This is when temperatures generally fall into the mid 50's across inland portions of the Nature Coast and below 60 degrees elsewhere across West Central and Southwest Florida. The only exception is near the coast, where the water keeps temperatures higher and these areas take longer to fall below 60 degrees.
