Spring Frost and Freeze Info - Including Statistical Dates of Last Occurence

Above normal temperatures throughout much of March and April has led to an early onset to the growing season across north-central and northeastern South Dakota and west-central Minnesota.  In fact, the growing season in many locations may be as much as 1 to 2 weeks ahead of normal.  As such, many folks may have taken advantage of these warmer conditions and started gardens or planting operations.  However, in many locations, freezing conditions are still possible this spring which may pose a threat to many agricultural interests (see dates below).

The NWS in Aberdeen issues several products to alert users for the potential for frost or freeze conditions. The following products will begin to be issued on (and after) May 7th:

Freeze Watch:   Issued when conditions are favorable for temperatures to fall below 32 degrees Fahrenheit during the next 12 to 48 hours resulting in the possibility for significant damage to unprotected vegetation. 

Freeze Warning: Issued when confidence is high that temperatures will fall below 32 degrees Fahrenheit within the next 24 hours resulting in significant damage to unprotected vegetation. 
Frost Advisory: Issued when conditions are favorable for temperatures to drop between 33 and 36 degrees Fahrenheit resulting in the possibility of widespread frost near the surface. Unprotected vegetation may be damaged.

Statistical Dates of the Last Spring Frost/Freeze

To assist the agriculutral community, below is a table that summarizes the last calendar day when temperatures of a given threshold are expected to be met. For example, in Aberdeen, the average (or mean) date when temperatures are last expected to fall to 32F occurs on May 13th.  Similarly, 90 percent of time, temperatures in Aberdeen will have fallen at or below 28F by May 18th.


ABERDEEN   36F 32F 28F 24F
  90th 7-Jun 27-May 18-May 9-May
  75th 29-May 19-May 12-May 1-May
  50th 24-May 13-May 3-May 19-Apr
  Mean 23-May 13-May 3-May 21-Apr
PIERRE   36F 32F 28F 24F
  90th 27-May 16-May 10-May 4-May
  75th 20-May 13-May 2-May 24-Apr
  50th 13-May 7-May 23-Apr 14-Apr
  Mean 13-May 5-May 25-Apr 15-Apr
WATERTOWN    36F 32F 28F 24F
  90th 11-Jun 1-Jun 20-May 10-May
  75th 4-Jun 24-May 12-May 2-May
  50th 25-May 16-May 4-May 21-Apr
  Mean 26-May 16-May 4-May 23-Apr
MOBRIDGE   36F 32F 28F 24F
  90th 1-Jun 22-May 15-May 29-Apr
  75th 24-May 14-May 7-May 28-Apr
  50th 17-May 9-May 28-Apr 15-Apr
  Mean 18-May 8-May 29-Apr 18-Apr



Mike Fowle - SOO

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