USDA Forest Service

North Central Research Station

Spring Freezes

Spacial patterns of growing-degree-day (GDD) threshold dates, average freeze temperatures following the GDD threshold dates, average number of freeze occurrences following the GDD threshold dates, and the average freeze dates after reaching the GDD thresholds for the North-central and Northeastern US can be viewed choosing the appropriate map icon via the table below.  The temperature data used for generating these maps were obtained from the National Climatic Data Center and are based on data for the period 1961–1990.

Freezes occurring late in the spring can damage tender new growth on plants, as well as kill developing insects and other animals.  What exactly qualifies as late depends on the species of interest.  For example, walnut trees may be fully leafed out in early May, while oak trees might not begin leaf-out until late May or early June.  Consequently, freezes that strike in mid-May would not harm oak, but may harm the walnut.

How the maps were made.

 
 Threshold  Threshold
Date		 Freeze
Temperature		 Number of
Freezes		 Freeze
Date
50 GDD 50 GDD Threshold Date Freeze Temp after 50 GDDs Number of Freezes after 50 GDDs Freeze Date after 50 GDDs
100 GDD 100 GDD Threshold Date Freeze Temp after 100 GDDs Number of Freezes after 100 GDDs Freeze Date after 100 GDDs
150 GDD 150 GDD Threshold Date Freeze Temp after 150 GDDs Number of Freezes after 150 GDDs Freeze Date after 150 GDDs
200 GDD 200 GDD Threshold Date Freeze Temp after 200 GDDs Number of Freezes after 200 GDDs Freeze Date after 200 GDDs
250 GDD 250 GDD Threshold Date Freeze Temp after 250 GDDs Number of Freezes after 250 GDDs Freeze Date after 250 GDDs
300 GDD 300 GDD Threshold Date Freeze Temp after 300 GDDs Number of Freezes after 300 GDDs Freeze Date after 300 GDDs
350 GDD 350 GDD Threshold Date Freeze Temp after 350 GDDs Number of Freezes after 350 GDDs Freeze Date after 350 GDDs
Note:  1 GDD (growing degree day) is the equivalent of 1 degree of temperature maintained for 24 hours above the specified base temperature of 5 degrees Celsius.  The color scale for each image is set to increase the contrast for that image.  Because of this, one must take care to consider the individual color scales when comparing two images.
 

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USDA Forest Service - North Central Research Station
Last Modified: January 26, 2005