Climate of the Tampa Bay area

Cumulus clouds building over the Tampa Convention Center on a summer afternoon

The warm and rainy season typically begins in late May and runs through October.[5] Average high temperatures are in the low 90s °F (around 32 °C) with lows in the mid-70s °F (around 24 °C) during this period, and the combination of warm temperatures and high humidity brings an almost daily chance of rain and thunderstorms, especially in the afternoon. Day-to-day weather is remarkably consistent, with summertime average highs and lows within five to ten degrees of the record high and low for any given date.[6]

In the typical summertime weather pattern, the combination of daytime heating and the interaction of the Gulf and Atlantic sea breezes creates thermal-fueled cumulus clouds over the Florida peninsula. These can produce rain showers or grow into towering thunderheads, either of which tend to drift westward on upper level winds produced by the Bermuda high, a semi-permanent weather feature over the Atlantic Ocean that strengthens during the summer months.[5] These storms can form anywhere across Central Florida from the interior near Orlando to along the west coast, depending on the wind and local weather conditions. Wherever they develop, Tampa's most common summer weather pattern results in afternoon thundershowers that usually rain themselves out by sunset, though on occasion, a storm cell will persist and drift west to the Gulf of Mexico to produce nighttime lightning displays visible from local beaches.[3]

A less common summer weather pattern is for prevailing westerly winds to cause overnight thundershowers to form offshore along a land breeze front. These storms bring morning rain to the Tampa area before moving inland later in the day, reversing the more typical timing. While afternoon storms are usually followed by a clear and cooler evening, morning rain often results in higher than usual humidity levels and the possibility of more storms developing in the afternoon.[5]

Summer storms typically bring brief periods of heavy rain and gusty winds with frequent cloud-to-ground lightning. They can grow severe, bringing strong straight-line winds, small hail, and torrential rain, and an occasional tornado. (While Florida sees the highest number of tornadoes per square mile of any state, the majority are small, weak, and short-lived compared to those seen in mid-western states.[7]) Waterspouts sometimes form when outflows from adjacent storm cells interact and begin to rotate over water, creating a funnel cloud over Tampa Bay or off the gulf beaches. These features usually stay offshore but occasionally reach land as a short-lived weak tornado.[8]

The Tampa Bay area is sometimes referred to as the "Lightning Capital of the World" for its frequent thunderstorms.[9] Though Central Florida receives as much lightning during the summer months as the world's true lightning leaders such as the Lake Victoria region of Africa and the central Amazon River Basin, thunderstorms are much less common from about October to May, so the area from Tampa to Orlando is more accurately deemed the "Lightning Capital of North America".[3][10] An average of about a dozen people are killed by lightning in Florida every year, with several annually in the Tampa area.[11], and TECO Energy, Tampa's primary electric utility, spends several millions dollars annually to repair transformers and other equipment damaged by lightning strikes.[12] University of Florida lightning expert Martin A. Uman has calculated that the average resident is within a half-mile of 10 to 15 lightning strikes every year.[13]

Coconut palms at the Gizella Kopsick Palm Arboretum in northeast St. Petersburg.

The dry season often begins in early November and can last into early May. The local weather during these months is normally sunny, mild, and quite dry, with a general cooling trend through the fall and a slow increase in temperatures starting in February. Highs during the coolest part of the winter average around 70 °F (21 °C), usually with sunny skies. The occasional passage of a cold front will bring rain followed by a few days of cooler temperatures.[3] Lows rarely reach freezing 32 °F (0 °C), an occurrence which happens, on average, once every other year in areas away from the water and less frequently in areas on Tampa Bay or the Gulf of Mexico.[3] While deep freezes are very infrequent, serious cold snaps are a significant concern due to the diverse range of freeze-sensitive agriculture and aquaculture industries in the area as well as tropical landscaping such as coconut palms and royal palms.

Frozen precipitation is very rare in the Tampa Bay area. The only known measurable snowfall in Tampa after 1900 occurred on January 19, 1977. While the accumulation amounted to less than 0.5 inches (13 mm), the city is so unaccustomed to snow that public schools closed for the day and many businesses and roadways closed until it melted away that afternoon.[14] Many residents of southern Pinellas County reported a light snowfall on December 23, 1989. However, no snow fell at official weather stations, and the weather record indicates that light sleet fell on St. Petersburg that day.[15]

The winter of 2009–2010 was one of the coldest in local history. Both Tampa and St. Petersburg set records for consecutive days in which the high temperature did not reach 60 °F (16 °C), and Tampa experienced ten consecutive days with a low temperature below freezing.[16][17] Much of the area received a "wintry mix" of rain and sleet on January 9–10.[18]

According to The Weather Channel, Tampa's all-time record low temperature is 18 °F (−8 °C) and St. Petersburg's is 20 °F (−7 °C), both occurring during the same cold snap on December 13, 1962.[19]

During El Niño, the Tampa Bay area receives cooler and wetter conditions during the dry season while during La Niña, the Tampa Bay area becomes drier and warmer than normal.

Due to the frequent summer thunderstorms, Tampa has a pronounced wet season, receiving a yearly average of about 30 inches (760 mm) of rain from June to September but only about 19 inches (480 mm) during the remaining eight months of the year combined. The historical averages late in the wet season are augmented by the passage of tropical cyclones, which can drop several inches of rain in just a few hours. Outside of the summer rainy season, most of the area's precipitation is delivered by occasional weather fronts - cold fronts often bring brief but intense rain while warm fronts tend to bring light rain over longer periods of time.[12]

Precipitation and temperature averages for the city of Tampa itself tend to fall near the median for the area. Communities to the interior tend to receive a bit more rain and experience slightly wider temperature fluctuations, while those on the Gulf coast tend to receive a bit less rain and less pronounced temperature differences, both in a single day and through the year.[20]

The area receives plentiful sunshine throughout the year, averaging a total of 2920 hours, or 66.7% of the possible total.[21] The daily sunshine amount is highest in May, when the sun's angle of incidence brings more hours of daylight but the rainy season has not yet begun.[21]