Many temperate fruit plants have a chill requirement in order to come out of dormancy and grow and fruit normally in the following spring. In our case, a chill hour is defined as each hour below 45℉. These are added together to get the number of chill hours. Some fruit plants can have a high chill hour requirement (like some apples, cherries, etc.), whereas others can be low to none (some peaches, blueberries, grapes, etc.). Another model tallies the hours when temperatures are between 45℉ and 32℉. Both are given for purposes of comparison. The most accurate measurement of chill hours is from a device within a field of interest. Although the data within this application is based on actual measurements, it should be used as a general guideline and not as an exact value because weather can vary from location to location. Some variation at the same location may occur for multiple recalls of the data. The reason for this is that the data being accessed is freely available and may have slight instability when it is retrieved. Thus, it is important to remember that these chill hour results are estimates. Multiple runs could be done and averaged if desired; however, the percentage difference is usually small and of little consequence. This app has been created to help Mississippi fruit growers assess growing conditions that impact plant physiology and to help them prepare for events in the upcoming season. For technical support, please contact the Extension Center for Technology Outreach. If you have questions or comments, please contact Eric Stafne.
A map of long term chill hour averages for Mississippi and other states can be found HERE
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