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Rainy season is coming, Tampa Bay. Here’s the official start date

Local meteorologists pushed the NWS Ruskin office to find average dates that defined the region’s rainy season.
The rainy season for Tampa Bay is set to officially begin on May 25 and continue until Oct. 10.
The rainy season for Tampa Bay is set to officially begin on May 25 and continue until Oct. 10. [ MARTHA ASENCIO RHINE | Times ]
Published May 14

Those in Tampa Bay already know: Summer is defined by heat, humidity and daily showers.

And summer is nearly here. The National Weather Service’s Ruskin office released dates outlining the start and end of the “rainy season” for the first time Tuesday: May 25 to Oct. 10 for Tampa Bay and from May 15 to Oct. 15 for the Southwest Florida area.

The announcement came two weeks after a conference call with local media and meteorologists, who pushed the agency for an exact time period when the region experiences the most rain.

The dates were created using data dating back to 1981 and comparing daily averages to predict when the rain is most likely to come in droves.

The results aren’t that surprising. Tampa Bay experiences an average of just 2.03 inches of rain in April and 2.10 in May. By June, that average shoots up to 6.68 inches.

“It’s a drastic jump from May to June,” said Meteorologist Rodney Wynn with the National Weather Service in Ruskin. “Then it stays steady there into September.”

The average rainfall for Tampa Bay in July is 7.07 inches, followed by a slightly wetter August at 7.77 inches. The total rainfall begins to dip from there, with an average of 6.3 inches in September.

By October, rainfall is back down to 2.26, according to the National Weather Service.

Tampa Bay still has two weeks before the rainy season officially commences. But the newly-formed dates only represent averages, Wynn said. Droughts and tropical storm systems have the ability to shake up averages on a month-by-month basis. A major hurricane can drop a month’s worth of rain in a single day.

WTSP-Channel 10 Meteorologist Ric Kearbey said the season can be broken down into three sub-seasons. May through early July is the “stormiest” part of the rainy season, he said, with the most damaging winds, waterspouts, tornadoes, excessive lightning, hail and flooding rain. That period is followed by a quieter July, August and early September, but still expect daily showers.

From mid-September to early October is when rainfall can be unpredictable — with early autumn cold fronts and tropical systems playing a factor, Kearbey said.

While impossible to predict exactly where storms will strike months in advance, a forecasted active hurricane season could play a leading role in rainfall totals this year. The Atlantic hurricane season begins June 1 and peaks in September.

Related: 2021 hurricane forecast: 17 storms, 8 hurricanes, 4 major ones

The first major forecast of the season calls for 17 named storms, eight hurricanes and four major hurricanes, according to Phil Klotzbach, one of the world’s top hurricane forecasters at Colorado State University. There is a 45 percent chance a major hurricane could strike Florida or the east coast this year.

“Summer brings the most rain to our region, without a doubt,” Wynn said. “Even an above-average month at another time of year doesn’t come close to summer totals.”