evaporative cooling

Avoid Evaporative Cooling in Citrus Freeze Protection

Daniel Cooperfreeze, Weather

evaporative cooling
Weather station in Florida field

Both University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) speakers at a Nov. 28 winter weather workshop warned about the risk of evaporative cooling when using irrigation to protect citrus from freezing temperatures. Microsprinkler irrigation has been the main form of cold protection for Florida citrus for at least the last five decades.    

The need to understand evaporative cooling was a key point that multicounty citrus Extension agent Chris Oswalt made about the use of microsprinkler irrigation for freeze protection. He also suggested that microsprinklers be placed on the north/northwest side of the tree within 3 feet of the trunk, and that water from emitters be aimed at the tree to protect the bud union.

Rick Lusher, project manager of the UF/IFAS Florida Automated Weather Network (FAWN), warned that “evaporative cooling may result in plant damage when water is used for cold protection during dry, windy conditions.”


Oswalt noted that all raw data used in making weather forecasts comes from the National Weather Service (NWS). A short video he showed explained how the NWS collects weather data by releasing weather balloons twice a day from 91 stations in the United States. The NWS also releases the balloons daily from more than 800 stations around the world. The balloons climb to a height of 35 miles during a typical two-hour flight. The information gathered by the balloons is used to forecast weather changes.

Growers considering using private weather forecasting services should ask those services if they have experience in agricultural weather, Oswalt advised. “It doesn’t matter where you source your weather information,” he said. “Consistency is the key as related to your location.”


Lusher reported that FAWN now has 47 sites in Florida that provide weather data, information and tools for cold protection, irrigation and chemical applications. He explained how FAWN’s Cold Protection Toolkit can help growers make irrigation decisions on cold nights.

Freezes are a potential threat to citrus every winter. Numerous freezes drastically reduced Florida’s citrus acreage in the 1980s. More recently, a Christmas 2022 freeze damaged many young trees in southern Georgia. Multicounty citrus Extension agent Mongi Zekri hosted the virtual winter weather workshop.

About the Author

Ernie Neff

Senior Correspondent at Large

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