Goodbye to Tampa Bay’s steamiest summer on record
Jeff Berardelli is WFLA's Chief Meteorologist and Climate Specialist
As autumn officially begins, we put summer in our rearview mirror. And for good reason! It was not only one of the wettest in Tampa history, it was also the most muggy.
Both Tampa and St Petersburg broke records for the highest number of days with a dew point at 80 degrees Fahrenheit or above. We typically only hit the sweltering 80-degree mark several times a year — but recently it happens much more often due to a warmer/more moist climate.
The dew point is an absolute measure of moisture in the air. Simply, the higher the number, the more moist the air is. Average mid-summer dewpoints are in the mid-70s. That's humid enough. Once numbers reach the upper 70s it is uncomfortable. And once they surpass 80, it can be hard to breathe.
In St. Petersburg, there were 57 days (almost two full months) where dewpoints reached 80 or above. That beats the record set last year of 55 days. And it smashes the long-term average of just 10. That means St Petersburg saw about six times its normal number.
In Tampa (Tampa International Airport) there were a record 31 days with dew points surpassing 80. That breaks the former record of 27 set in the Super El Nino year of 1998. The long term average is only 5.
The fact that the air is getting more muggy is no surprise. This is due directly to human-caused climate change from the burning of fossil fuels and release of heat-trapping climate pollution. Simply, warmer air holds more moisture. So as the temperatures increase, so does the amount of moisture in the air.
Along with the air heating, the Gulf of Mexico is also getting hotter. That means the overlying air gets more humid and creeps into Tampa's coastal areas.
Back in the 1940s through 1970s the average dewpoint during the heart of summer was 72. Then in the 1980s and beyond the number steadily increased. The past two years have been especially brutal with the mid-summer dewpoint ranging from 75-76. That's about a 4-degree dewpoint increase in just the last 50 years.
The result of this is two-fold. First, more moisture in the air means that the most extreme rainfall events have rain rates that are heavier than normal, causing historic flooding. We vividly remember that a few times this summer.
Next, it creates more oppressive heat index days. As you might expect, this summer was a record breaker for this too. In Tampa, 92 days featured a heat index of 100 degrees or higher. This beat the old record of 88 set last summer. The long term average is less than half of that — only 40 days.
Going back to before humans had a big impact on the climate, the 1950s and 60s, Tampa only averaged 20 days with a heat index of 100+. As seen below, in recent years we have more than quadrupled that.
If I told you this heat and humidity is the new normal, I doubt that would come as a surprise to you. But it's only half true. There is no new normal. As long as we continue to warm the Earth, summers will continue to get more sweltering and even dangerous.
The summers of the 2020s will likely be the coolest summers you will ever experience again. And the only way to stop it is for humanity to shed it's addiction to burning fossil fuels and arrest the heating.
