Climate
Florida is uniquely situated geographically so that the state has an enormous range of climatic conditions most of which are unique relative to the remainder of the United States.
Major driving factors for Florida's weather are global air circulation patterns, geography consisting of low elevational, near-coastal lands along the Gulf of Mexico and a peninsula and islands extending south into the Caribbean.
Most of peninsular Florida is in a latitudinal band that, globally, is often desert. Florida is saved from this fate by being a peninsula surrounded by water. Rising air, caused by heating of the land surface, causes moist sea breezes to flow in from the coasts toward the center of the state triggering thunderstorms and causing a summer rainy season. During the winter and spring months, when water off the coast is warm relative to the land and there is less heating of the ground surface, the effect of the water is actually reversed, and rainfall tends to be suppressed causing a distinct dry season. Cold northern air passing over water is warmed, and the peninsula is also protected from the extremes of cold temperatures during the winter.
North Florida extends into more temperate regions. Summer thunderstorms are less frequent (at least sometimes!), but relatively more of the temperate zone frontal systems pass across the area. A higher frequency of frontal passages during the cooler months gives north Florida a rainfall peak in the winter, and depending on location, a bimodal rainfall distribution on an annual basis. The fronts also bring in exchanges of warm and cold air, giving north Florida greater short-term temperature fluctuations. Without the protection of water to the north, cold winter air masses receive much less amelioration before they reach the area.
From a plant perspective, this results in a gradual shift, from north to south, of conditions suitable for mid-temperate zone species, to species associated with the subtropics.
The summary maps below are from the Florida Climatic Center at Florida State University (FSU). Click on the small map to get a larger image. If you go to their web site, you can find additional information on the various indices mapped
| Heat Hardiness Index | Cold Hardiness Index | Mean Annual Precip. | Winter Precip. | Annual Thunderstorms |
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We speak of typical and average conditions, but "average" in Florida is a misnomer. There is a broad range of "normal" conditions, and presence of a variety of "extreme" weather phenomena is an important part of that norm.
Drought and Flood
Both drought and flood are part of the normal climatic pattern. From a global perspective, many of Florida's drought periods originate from the "El Nina" weather phenomenon that develops in the southern Pacific and which influences weather world-wide. In Florida, the major symptom is winter drought. Luckily, we still get that typical summer rainy season, but during these drought periods, it does not make up for low winter rainfall.
Drought is balanced by other periods, often associated with the south Pacific "El Nino" phenomenon, which results in high winter rainfall in Florida. We may go from too dry to too wet - or so it seems from an anthropomorphic perspective. Species which live here are adapted to these extremes. Florida also gets major rainfall on a large-scale but regional basis from hurricanes.
Freezes
Below-freezing temperatures are more likely to occur inland and to the north. Even just a short distance from the sea, an area at one latitude might be twice as likely to get a freeze than along the coast, so tropical species tend to occur in a band along the coast around the tip of southern Florida. Between 1930 and 1979, Key West was the only place in Florida that did not experience below-freezing temperatures. Freezes limit the northern extent of tropical species. Lack of cold also limits the southern extent of some northern species - extraordinary measures are required to grow northern spring bulbs and fruit trees in central and southern peninsular Florida in part because the cold requirements, usually associated with breaking dormancy and flowering, are not met.
Hurricanes
Hurricanes are most likely in September and October, when the ocean temperature is warmest and humidity highest. Annually, over a hundred tropical waves develop in the Atlantic, Caribbean, and Gulf of Mexico, although fewer than ten develop into tropical storms, and only a handful become hurricanes. The coastlines from Florida Bay to Melbourne, and Pensacola to Panama City, have the highest risk of hurricanes, averaging one every six to eight years.
Hurricane winds reach their highest velocity in the right front quadrant of the storm. Tornadoes may be generated, particularly in this quadrant of the storm. Hurricane flooding can be caused by high rainfall, storm surge, and high waves due to winds. Typically, we think of hurricanes as destructive, but ecologically, they are normal phenomena that are important to maintaining the water/drought balance and also in periodically opening up forests for regeneration. The storm surges, which invoke much human angst, are hugely important for reconfiguring coastal islands and dunes and providing a periodic dose of salt to higher coastal marshes thus eliminating species intolerant of salt from those areas.
Lightning and other Thunderstorm Phenomena
Most summer thunderstorms are triggered by air rising off of a heated surface. In peninsular Florida, they often occur in the afternoon, especially where the sea breezes from the east and west coasts meet. Florida has more than 90 "thunderstorm days" per year. This means that at any one spot in the state, there will be a thunderstorm within about 15 miles at least 90 times per year on average. Most thunderstorms occur in July and August, and are most frequent in central Florida around Tampa, Lakeland, and Fort Myers. Thunderstorms also occur along frontal boundaries, especially cold fronts, where warm air is forced up over a wedge of incoming cold air.
Ecologically, lightning is an extremely important phenomenon. Lightning caused fires were (and are) a normal phenomenon. Most of our native species are adapted to fire, and in many cases, the locations where they grow are determined by fire regime. Many species bloom only after fire. Historically, most lightning-caused fires occurred early in the rainy season before vegetation and soils were well hydrated. They burned across broad areas. Today, the landscape is broken up by fields, roads, houses, etc., so lightning fires individually burn less acreage and we often need to conduct controlled burns both the reduce severity of fires when they occur and to re-introduce fire into landscapes that no longer burn with adequate frequency.
High winds are another ecologically important phenomena associated with thunderstorms. Tornadoes, gust fronts, and severe downbursts have the capacity to down trees and cause localized disturbances in the natural landscape, often opening up forests for regeneration.
Links
A page of text is totally inadequate to explain Florida's weather and how it relates to the ecology of natural systems. The links below can provide more information
