Warm Winters And Early Spring? Late Freeze/Frost Still Probable.

With the recent record warm and the prospects for a continued warm pattern dominating the region's weather, home gardeners, outdoor enthusiasts and the like are looking forward to spring. Seed catalogs on the coffee tables, area greenhouses stocking supplies have those ready for the growing season to get underway. Yet, does a warm winter translate to an early spring? Is the risk of frosty or freezing weather over? Not yet! Statistics show that cold weather comes, sometimes quite late, even after a long stretch of warmer than normal weather. The Midwest Regional Climate Center in Campaign Illinois has an excellent analysis of the early warmth and climatology of spring freezes, which can be found here.

In fact, based on a search of the historic record it looks as though there is an enhanced risk of later than normal cold snaps following a warm winter season. Below is a table of the average last hard freeze, freeze and frost for selected cities across eastern North Dakota and northwestern Minnesota. The three columns represent the 1981 - 2010 preliminary dates for the [average] last frost, freeze and hard freeze.

As one can see by the table below there is quite a bit of variability from location to location. For example, the last recorded 38F or colder at Detroit Lakes is listed as June 4 while the latest at Crookston - farther north - is May 30. Whats up with that? As the old Real Estate axiom goes "Location, Location, Location". The Cooperative station near Detroit Lakes is located in a slightly more rural area, while the Cooperative station at the Crookston Experimental Station reflects a bit more urban environment.

 

                  Equal to or less than                      Equal to or less than
City             28F      32F      38F      City            28F     32F     38F     
Cavalier 7NW     May 5    May 16   May 30   Ada             Apr 29  May 9   May 25  
Edmore 1NW       May 9    May 20   June 12  Agassiz WLM     May 4   May 12  May 17  
Fargo Hector     May 2    May 8    May 24   Crookston Exp   Apr 30  May 10  May 30  
Forman 5SSW      Apr 26   May 6    May 22   Detroit Lakes   May 2   May 16  June 4  
Grand Forks Arpt May 2    May 12   May 31   Georgetown 1E   May 1   May 9   May 27  
Hansboro 4NNE    May 11   May 21   June 6   Thorhult        May 14  May 28  June 13 
Lisbon           May 1    May 9    May 27   Thief Rvr Falls May 6   May 18  June 3  
Petersburg 2N    May 3    May 18   June 1   Wadena 3S       Apr 30  May 9   May 28  
Valley City 3NNW May 5    May 12   May 30   Warroad         May 5   May 15  June 1  

Note: This data is provisional based on preliminary information and subject to change. Updated data from the National Climate Data Center will be released later this year.

What about this year? We've had record warm weather the past 6 months, and despite the recent cool down we're still seeing temperatures above normal on most days. Research suggests that despite the warm weather, late freezes and frosts are still possible. In fact, we've seen temperatures cold enough for frost in every month! Below is a table with the ranking for the warmest meteorological winters and the date of the last day that year the air temperature fell to 38 degrees, a temperature cold enough for surface frost to form.*

Fargo Area  (ThreadEx Station) Extremes
Highest Average Average Temperature degrees F
Days: 12/1 - 2/29
Length of period: 91 days
Years: 1881-2012
                                                                                                          
Rank  Value  Ending Year      Last <32F <38F
  1    22.1    2012           *****     *****
  2    22.0    1987           Apr 22    May 22
  3    21.7    1931           May 22    June 7
  4    20.7    1998           Apr 22    June 7
  5    20.1    2002           May 24    May 24
  6    19.5    1992           May 24    June 7
  *    19.5    1983           May 25    May 25
  8    17.8    2000           May 14    May 15
  9    17.6    1944           May 8     May 8
  *    17.6    1942           May 14    June 13
                                                                                                          
Ending Date is the last day of the 90-day period.Only periods with no missing data were evaluated. This station's record may include data from more than one, possibly incompatible, locations. It reflects the longest available record for the Fargo Area.
                                                                                                          
GRAND FORKS UNIV (323621)Extremes
Highest Average Average Temperature degrees F
Days: 12/1 - 2/29
Length of period: 91 days
Years: 1890-2012
                                                                                                          
Rank  Value  Ending Year      Last <32F <38F
  1    21.2    2006           May 5     May 21
  2    20.0    1983           May 25    June 5
  3    19.9    1987           Apr 22    May 22
  4    19.4    2012           *****     *****
  5    19.3    1998           May 3     June 8
  6    19.0    1931           June 7    June 7#
  7    17.8    2002           May 24    May 27
  *    17.8    1992           May 4     May 24
  9    17.3    2000           May 15    June 5
 10    15.9    1981           May 10    May 30
                                                                                                          
Ending Date is the last day of the 90-day period. Only periods with no missing data were evaluated. #-Temperature did not drop below 38 again that month. The UND/NWS Cliamte Station was used to reflect the longer data period.

* Frost may form at air temperatures above freezing when skies are clear and the wind calm. Air temperature is measured at approximately 6 feet above ground level, and with light winds the air just above the surface can by 5 to 10 degrees colder than at the level of the sensor.

Then what does this all mean for this spring season? Despite the record warmth of the past 6 months, the current outlooks suggest an increase in storminess across the region with the attendant general cooling trend wetter than average weather often brings. History shows that the odds favor a hard freeze - temperatures below 28 degrees or colder - at least into early May. So before you get that garden planted, keep an eye on the forecast and keep reading those seed catalogs.

For more information please contact Mark Ewens at the Grand Forks NWS, 701-795-5198 or email at Mark.Ewens@noaa.gov 



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