The frequency of freeze events in subtropical blueberry growing regions in Florida

Freeze events during January and February can result in major crop and economic losses for growers of low-chill, early-ripening cultivars of blueberry (Vaccinium spp.) in Florida. Overhead irrigation for freeze protection is commonly used by growers to protect their crop from freeze events. Freezes are typically categorized as either radiative or advective, each with their own set of risk parameters. The objective of this research was to use historical weather data to provide growers with additional information for their selection of passive and active freeze protection strategies to mitigate risk. Three sites in Florida were chosen as representative of major blueberry growing regions and weather data from 2000-2015 were downloaded from the Florida Automated Weather Network (FAWN) and analyzed. Hourly temperature, wind speed, and relative humidity were used to determine the average of number of days per month with sub-zero temperatures, the average duration of freeze events, and to classify each event as a radiation, advective, or mixed freeze. Radiation freezes were the most common type of freeze event in Alachua County, Florida, whereas Polk County has fewer freeze events including some years without sub-zero temperatures, without a clear prevalent freeze event type. Ultimately, the frequency and severity of freeze events, based on historical data, can be used to further inform grower investments in freeze avoidance and protection.