Now that we’re at the autumnal equinox it’s time to cool down, right? Not so fast.

The most popular question I get this time of year: “When will we get the first cold front?'

I agree that it’s always nice to feel that first front take an edge off the heat. But because we live in a sub-tropical climate, our Summer season typically starts about a month earlier and ends about a month later than locations to the north. With that in mind, ignore the calendar start to autumn. We rarely cool down around here in September.

Let’s dive into our climate folder to see what’s normal for the Tampa Bay area this time of year:

  • Observation #1: The first cold front of the season is usually weak, with just enough dry air to drop our humidity and bring our rainy season to an end. But it rarely drops our temperatures that much. Generally speaking, the first front will drop our highs from the low 90s to the upper 80s. That’s about it. But it tends to feel more comfortable because of lower humidity and slightly cooler lows at night that drop into the 60s.
  • Observation #2: That first front usually only changes our atmosphere briefly and we tend to warm right back up after a few days. It usually then takes a second or even third front later in October to early November before our temperatures more permanently drop and stay down in a lower range for the rest of the year.
  • Observation #3: Large scale weather patterns play a big role in our autumn season. There were many years where the tropics were very active in autumn, and we tended to get a push of cooler, drier air sooner in most of those years. There were many years where the weather was tranquil with relatively dry conditions, but the downside was it took a long time to get the first blast of cooler air (2015 was actually like that). Then there were years where the autumn was really wet with numerous fronts making it down into our area early but they would stall out. That would lead to below average temperatures due to all the clouds and rain, but the fronts wouldn’t actually push through. So it would lead to a prolonged rainy season, but no relief from the high humidity. It was interesting to see that these patterns repeated themselves over and over again through the past 100 years. So although no autumn is exactly like the last one, there are definitely patterns that we can see show up time and time again.
  • Observation #4: It’s not always a good thing to get an early season front. In some of the years when we got an early season front in September it resulted in a tropical storm coming near our area. A good example of this was in 2001 when Tropical Storm Gabrielle came right at us from the Gulf due to a cold front moving in from the north. That was on September 14. A lesson to be learned is that although we might want cooler air, sometimes it’s better to stay warm longer than to get a tropical threat barreling right at us due to a cold front.
  • Conclusion: If you average in all the early fronts with all the late fronts over the years, you get a general median of somewhere in early to mid October.

Some recent memorable autumn cold fronts:

  • October 9, 2000: Strong front moves through with a high of only 70 degrees -- a record for the coolest it’s ever been on that day. Record lows were in the upper 40s to low 50s that night.
  • October 24, 2005: Hurricane Wilma makes landfall to our south, pulling colder air down into our area. Highs dropped from 90 before the storm to 68 after the storm. Lows at night dropped into the upper 30s to mid 40s.
  • September 25, 2008: Strong front with a high of only 82 and record morning low of 65 in Tampa.
  • October 1, 2009: High of 83 with lows in the 40s for northern counties. But just 4 days later highs were back up to 90 with muggy lows of 79. There was a record high of 92 on the 11th followed by record cold on the 18th with a high of only 66!
  • September 13, 2015: First front of season drops us to 86 with lower humidity. But back to a high of 93 for the 20th. There was a small cool down from October 3 to 8 , but then warm, muggy air tended to stick around through the rest of the month into early November. Had a record high of 92 on November 4. Finally got a stronger front in mid November to bring in more comfortable conditions.