Climate of the Tampa Bay area

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

Tampa Bay is midway down the peninsula on the right. Small cumulus clouds cover the peninsula at about 1 PM on September 6, 2006. A tropical disturbance is on the far left.

The hot and wet season begins in May and lasts through October. Seasonal high temperatures average about 90s °F (around 32 °C) and lows in the mid-70s °F (around 24 °C), accompanied by high humidity and an almost daily chance of thundershowers, especially in the afternoon. Day to day weather is remarkably consistent, with wet season average high and low temperatures usually only about five degrees above or below the record highs and lows.[4]

The typical summer weather pattern is for heat-produced thermals, powered by either the Gulf or Atlantic sea breeze (and occasionally both simultaneously), to build puffy white cumulus clouds into threatening thunderheads over the interior of the Florida peninsula. Usually, the resulting storms drift slowly westward to the bay area, though they may rain themselves out before reaching Tampa if the easterly winds are light or the sea breeze from the Gulf of Mexico is too strong. Stronger storm cells often survive to move out over the Gulf of Mexico, where they can be seen from the beaches as spectacular nighttime lightning shows.[3] Occasionally, storms form offshore overnight along the land-breeze front which is the dermal counterpart of the daytime sea-breeze front. If the prevailing winds are from the west or southwest, these storms can push ashore into the Tampa Bay area in the morning and move inland, reversing the more common pattern.

Summer thunderstorms typically bring brief periods of heavy rain and gusty winds with frequent cloud-to-ground lightning. Afternoon storms are usually followed by a pleasantly clear and cooler evening, while morning storms usually bring very high humidity levels and a chance for more rain in the afternoon. At times, these storms can grow severe, bringing damaging winds, small hail, and torrential rain, and an occasional tornado. While Florida does rank #1 in the US in terms of tornadoes per square mile, the majority of the twisters are small, weak, and short-lived.[5] Waterspouts are relatively common in Tampa Bay and off the gulf coast during strong summer thunderstorms, occasionally moving onshore as a short-lived tornado.

Though the Tampa Bay area is sometimes referred to as the "Lightning Capital of the World",[6] it is more accurately called the “Lightning Capital of North America” if measured by average number of days with thunderstorm activity per year. During the summer, west-central Florida receives as much lightning as the world's true lightning leaders such as the Lake Victoria region of Africa and the central Amazon River Basin. However, there are few thunderstorms in the Tampa Bay area from approximately October to May, decreasing the yearly average.[3]

Every year, Florida averages 10 deaths and 30 injuries from lightning strikes, with several of these usually occurring in or around Tampa.[7] 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.[8] TECO Energy, Tampa's electric utility, spends over millions of dollars annually to repair transformers and other equipment damaged by lightning strikes.[9]

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.[10] 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.[11]

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.[12][13] Much of the area received a "wintry mix" of rain and sleet on January 9–10.[14]

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.[15]

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 an average total of 28 inches (710 mm) of rain from June and September but only about 18 inches (460 mm) during the remaining eight months of the year combined. The historical averages during the late summer, especially September, are augmented by tropical cyclones, which can easily deposit many inches of rain in one day. Outside of the summer rainy season, most of the area's precipitation is delivered by the occasional passage of a weather front.[9]

Tampa's precipitation data falls near the median for the area. Nearby communities to the interior tend to receive a bit more rain every year; those closer to the coast a bit less.[16]

The area receives plentiful sunshine throughout the year, averaging a total of 2920 hours, or 66.7% of the possible total.[17] The daily sunshine amount is highest in May, when the sun's angle of incidence has increased the hours of daylight and the rainy season has not yet begun.[17]

The 2004 Atlantic Hurricane Season was historically busy for the Tampa Bay area. The region was affected by a record four hurricanes that year; Frances, Jeanne, Charley, and to a lesser extent, Ivan.[24] Jeanne and Frances passed over Tampa as tropical storms after making their way across the state from the east coast.[25][26] Charley was forecast to make a direct hit on Tampa Bay from the south-southwest, which would have been the worst-case scenario for local storm surge flooding.[27] But the storm made a sudden and unexpected turn to the northeast and brought only tropical storm force winds to the region, devastating the Ft. Myers/Port Charlotte area instead.[28][29] Ivan also threatened the area as it moved north up the eastern Gulf of Mexico. It remained far to the west of central Florida, however, and brought only a bit of rain and wind to Tampa Bay before eventually slamming into coastal Alabama and the Florida Panhandle.[30]