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• Florida's Hot Season by Morton D. Winsberg
• Climate of Florida (PDF) by Morton D. Winsberg

The Florida Climate Center and the Center for Ocean-Atmospheric Prediction Studies (COAPS) have been leaders in the research of climate variability in North America, particularly as related to the El Niño - Southern Oscillation (ENSO). Given that wildfire activity is intimately linked with temperature and precipitation patterns, it naturally follows that ENSO would also have an impact on annual wildfire occurrences. This relationship holds especially true for Florida and the Southeast United States, where there is a strong connection between ENSO and climate during the winter and spring months which overlaps the traditional wildfire season in this region.

COAPS first cooperated with the Florida Division of Forestry in a research project identifying the connection between ENSO and wildfire burn acreage in Florida. COAPS has since extended that research and developed a prototype wildfire risk forecast system for Florida and the Southeast under research grants from the Florida Division of Forestry and the USDA Forest Service.

The wildfire risk forecast is based on ENSO phase and the Keetch-Byram Drought Index (KBDI). The KBDI was developed by foresters in the Southeast and represents water available in the upper layers of the soil. The KBDI is used extensively in forestry and wildfire applications. The wildfire risk forecast gives monthly probabilities of the KBDI reaching critical values from January through July, coinciding with the traditional wildfire season in the Southeast. The forecast is released in January each year, and updated throughout the season. Results are available on www.agroclimate.org and are presented each year at the National Seasonal Assessment Workshop, sponsored by the National Interagency Coordination Center. Ongoing support for this project comes from the NOAA RISA program and USDA Risk Management Agency.

Contact David Zierden at This email address is being protected from spambots. You need JavaScript enabled to view it. for more information.

Images of snow and freeze events in Florida. Courtesy of Florida Memory.

Although many people head south to escape the cold in the winter, it isn't always warmer in Florida. When an intense low pressure system is followed by a strong high pressure system, particularly powerful invasions of cold air may occur in Florida. These cold air outbreaks can produce below-freezing temperatures and are usually accompanied by strong winds that can produce bitterly cold wind chills.

Over the past 150 years, numerous severe cold outbreaks have affected Florida. In February 1899, a cold wave that became known as the Great Arctic Outbreak pushed frigid Canadian arctic air into the state. During this event, the lowest temperature ever recorded in Florida (-2°F) occurred on February 13, 1899. Since this outbreak, a number of "impact freezes" have influenced the retreat of the famous Florida orange groves from areas around Jacksonville and St. Augustine to their current locations in south Florida. 

Contrary to popular belief, it does snow in Florida. The first documented account of snow in Florida was reported in 1774. During the Great Arctic Outbreak, which was responsible for one of the biggest widespread snow events in the state, snow measured up to 3 inches deep in numerous Panhandle communities, and snow flurries were reported as far south as Fort Myers. Since 1886, there have been more than 80 months in which at least a trace of snow has been reported somewhere in the state. 

Images of tornado damage in Florida. Courtesy of Florida Memory.

Truly destructive tornadoes are most frequently reported in Florida during the spring and summer; the most powerful usually strike in spring. Florida has the dubious distinction of having a higher frequency of tornadoes per 10,000 square miles than any other state, including Oklahoma! In Florida, measured in frequency of tornadoes for every 10,000 square miles, the coast between Tampa Bay and Fort Myers has a particularly high incidence, as do the western panhandle and parts of the Atlantic Coast.

So, what is a tornado? Simply put, a tornado is a violently rotating column of air that is spawned by a severe thunderstorm. It connects from the thunderstorm to the ground and often appears to have a funnel or column shape. A tornado, one of nature's most violent storms, can develop suddenly, and have winds in excess of 250 mph.

Generally, tornadoes in Florida form

1. along a squall line ahead of an advancing spring cold front from the North,
2. along the squall lines in areas where masses of warm air converge,
3. from isolated local summer thunderstorms, and/or
4. within a hurricane.

What triggers a tornado is still not altogether clear. Tornadoes spawn inside clouds when there is great turbulence and winds of various speeds and velocities come in contact with one another. Although there is uncertainty about the triggers, meteorologists are able to identify atmospheric conditions conducive to tornadic activity.

The intensity of a tornado can be determined only after the event when survey teams from the National Weather Service can examine structural damage. After the survey is complete, the tornado is given a value from the Fujita Scale. The Fujita Scale was developed by Dr. T. Theodore Fujita and categorizes tornadoes on the basis of their intensity and area. The scale relates a tornado's damage to the fastest quarter-mile wind speed at the height of the damaged structure to determine its intensity. Over the years, problems with the initial Fujita Scale had arisen and in 2007 the new Enhanced Fujita (EF) Scale was adopted. The EF Scale helps determine the intensity of a tornado when there is no structural damage (as can happen when, for example, a tornado passes through a corn field).