Groundhog Day History & Climatology

Around the fifth century, the European Celts believed that animals had certain supernatural powers on special days that were half-way between the Winter Solstice and Spring Equinox.  Folklore from Germany and France indicated that when marmots and bears came out of their winter dens too early, they were frightened by their shadow and retreated back inside for four to six weeks.  This was adopted by the Romans as Hedgehog Day.  When Christianity came into being, the formerly pagan observance also came to be called Candlemas.

The earliest known American reference to Groundhog Day can be found at the Historical Society of Berks County in Reading, Pa.  The reference was made Feb. 4, 1841 in Morgantown, Berks County (Pennsylvania) storekeeper James Morris’ diary: 

Last Tuesday, the 2nd, was Candlemas day, the day on which, according to the Germans, the Groundhog peeps out of his winter quarters and if he sees his shadow he pops back for another six weeks nap, but if the day be cloudy he remains out, as the weather is to be moderate.

The NWS groundhogs all saw their shadow of the morning of February 2, 2014.
The NWS groundhogs all saw their shadows this morning.  This means another 6 more weeks of winter.

In the U.S. the tradition derives from a Scottish poem:

As the light grows longer
The cold grows stronger
If Candlemas be fair and bright
Winter will have another flight
If Candlemas be cloud and rain
Winter will be gone and not come again
A farmer should on Candlemas day
Have half his corn and half his hay
On Candlemas day if thorns hang a drop
You can be sure of a good pea crop

How accurate is the groundhog?

In western countries in the Northern Hemisphere the official first day of Spring is about six weeks after Groundhog Day, on March 20 or 21.  About 1,000 years ago, before the adoption of the Gregorian calendar when the date of the equinox drifted in the Julian calendar, the spring equinox fell on March 16 instead.  This was exactly six weeks after February 2.  Assuming that the equinox marked the first day of spring in certain medieval cultures, as it does now in western countries, Groundhog Day occurred exactly six weeks before spring. Therefore, if the groundhog saw his shadow on Groundhog Day there would be six more weeks of winter. If he didn’t, there would be 42 more days of winter. In other words, the Groundhog Day tradition may have begun as a bit of folk humor.

Alternatively, the custom could have been a folk embodiment of the confusion created by the collision of two calendrical systems.  Some ancient traditions marked the change of season at cross-quarter days such as Imbolc when daylight first makes significant progress against the night.  Other traditions held that Spring did not begin until the length of daylight overtook night at the Vernal Equinox.  So an arbiter, the groundhog / hedgehog, was incorporated as a yearly custom to settle the two traditions.  Sometimes Spring begins at Imbolc, and sometimes Winter lasts 6 more weeks until the Equinox.

For more information on the various prognosticating groundhogs across North America click here


Groundhog Climate Statistics:

Below are some Groundhog Day weather statistics for La Crosse, WI and Rochester, MN.

La Crosse, WI:

The following statistics comprises 141 years of data. From 1873 through 1950, the data came from various locations in downtown La Crosse. Since 1950, the data has been gathered at La Crosse Regional Airport.

Groundhog Day in La Crosse, WI
(Period of Record 1873-2013)

Means
Records
Maximum Temperature
28F
Warmest High Temperature
51 F
February 2, 2006
Coldest High Temperature
-13 F
February 2, 1996
Minimum Temperature
10 F
 
Warmest Low Temperature
33 F
February 2, 2003
February 2, 1999
Coldest Low Temperature
-34 F
February 2, 1996
Average Temperature
19 F
 
Warmest Average Temperature
39.5 F
February 2, 2006
Coldest Average Temperature
-23.5 F
February 2, 1996
Precipitation
0.04"
Wettest
1.29"
February 2, 1983
Snowfall
0.3"
Snowiest
10.0"
February 2, 1983
Snow Depth
at 7 AM
6"
Most Snow of Ground
at 7 AM
29"
February 2, 1929

The odds of having any precipitation at all on Groundhog Day is 52.5% (74 out of 141).  There has been measurable (0.01" or greater) precipitation on 41 Groundhog Days and trace amounts (less than 0.01") of precipitation on 33 Groundhog Days.  Since 1893, it has snowed on 62 out of 121 (51.2%) Groundhog Days.  Measurable snow (0.1" or greater) has fallen on 32 Groundhog Days.  Since 1893, residents have woken up with measurable snow (half inch or greater) on the ground 104 times and trace amounts (less than a half inch) on 8 times.

In 2013, the high temperature was 13 degrees and the low temperature was 1 degree. 0.02 inches of precipitation fell.  This amounted to 0.9 inches of snow. There was 7 inches of snow on the ground.  The average wind speed was 9.8 mph.

Rochester, MN:

The following statistics comprises 114 years of data. From 1887 through 1931, the data came from several cooperative observers in the Rochester area. Since 1932, the data has been gathered at Rochester International Airport. No data was taken on Groundhog Day from 1890, 1891, 1908, 1909, from 1921 to 1928.

Groundhog Day in Rochester, MN
(Period of Record 1887-2013)

Means
Records
Maximum Temperature
25 F
Warmest High Temperature
48 F
February 2, 2012
Coldest High Temperature
-20 F
February 2, 1996
Minimum Temperature
9 F
 
Warmest Low Temperature
32 F
February 2, 2003
Coldest Low Temperature
-35 F
February 2, 1996
Average Temperature
17 F
 
Warmest Average Temperature
37.5 F
February 2, 2012
February 2, 2006
February 2, 1944
Coldest Average Temperature
-27.5 F
February 2, 1996
Precipitation
0.02"
Wettest
0.67"
February 2, 1983
Snowfall
0.3"
Snowiest
9.3"
February 2, 1983
Snow Depth
at 7 AM
7"
Most Snow of Ground
at 7 AM
21"

February 2, 1979

The odds of having any precipitation at all on Groundhog Day is 49.0% (49 out of 100).  There has been measurable (0.01" or greater) precipitation on 25 Groundhog Days and trace amounts (less than 0.01") of precipitation on 24 Groundhog Days.  Since 1929, it has snowed on 44 out of 85 (51.8%) Groundhog Days.  Measurable snow (0.1" or greater) has fallen on 23 Groundhog Days.  Since 1939, residents have woken up with measurable snow (half inch or greater) on the ground 67 times and trace amounts (less than a half inch) on 3 times.

In 2013, the high temperature was 12 degrees and the low temperature was 6 degrees.  0.04 inches of precipitation fell.  This amounted to 1.0 inches of snow. There was 2 inches of snow on the ground.  The average wind speed was 6.1 mph.


Groundhog Weather History:

Below are some weather events that took place on this day:

  • In 1951, a strong arctic cold front moved through central Wisconsin. Temperatures at Alma, WI fell from a high temperature of 41 to -12 by the end of the day. This 53 degree difference between the high and low temperature tied 3/22/1951 for Alma's greatest diurnal temperature change.
  • In 1956, Osage, IA received 6" of snow.
  • In 1965, Theilman, MN had its coldest February temperature (-38).
  • In 1970, a strong arctic cold front moved through the region. Temperatures ahead of the cold front were mainly in the 30s. Once the cold front moved through, temperatures fell throughout the day, falling below zero by the end of day. One of the greatest temperature changes occurred at La Crescent, MN. They had a high temperature of 38 and low temperature of -8. This 46 degree diurnal temperature difference is the greatest ever recorded there.
  • In 1973, Theilman, MN received 6" of snow.
  • In 1983, a snow storm brought heavy snows to the region: In IA: Oelwein (10"), Decorah (9"), Marble Rock (9"), Waukon (8.5"), Charles City (7"), Elkader (7"), Waucoma (7"), Fayette (6.1"), Osage (6"). In MN: Rochester (9.3"), Austin (8"), Grand Meadow (6"), La Crescent (6"), Minnesota City (6"). In WI: La Crosse (10"), Mondovi (9"), Hillsboro (8.5"), Cashton (8"), Mauston (8"), Muscoda (8"), Necedah (8"), Platteville (6.3"), Lancaster (6").
  • In 1996, record low temperatures for February were set in: Cresco, IA (-36, also coldest day on record), Austin, MN (-34), Osage, IA (-34, also coldest day on record), Charles City, IA (-32), and Lancaster, WI ( -31, also tied with 1/23/1963 for coldest day on record).
  • In 1998, a snow storm produced heavy snow in Alma, WI (7"), Harmony, MN (6"), Lanesboro, MN (6"), Neillsville, WI (6"), and Osage, IA (6") snow.
  • In 2004, an area of low pressure tracked northeast from the southern Plains on the 1st, to across the eastern Great Lakes by the 3rd. An inverted surface trough north of the low brought widespread snow to the region, with the bulk of the precipitation falling on the 2nd. The heaviest snow fell across southeast Minnesota and north central Wisconsin, with 8-12" common. Amounts south and east of there were in the 4-8" range. Some specific totals from the event: In IA: Osage (8.7"), New Hampton (8"), Charles City (7.5"), Mason City (6"), Oelwein (4.5"), Fayette (4.3"), Decorah (4"), Elkader (4"). In MN: Austin (12"), Grand Meadow (11"), Theilman (9.9"), Rochester (9.4"), Owatonna (8.5"), Preston (5.4"), Caledonia (5.3"), Zumbrota (5"). In WI: Mondovi (7.6"), Alma (7"), Hatfield (7"), Cashton (6"), Neillsville (6"), Viroqua (6"), La Crosse (5.9"), Genoa (4"), Lynxville (4"), Mauston (4"), Richland Center (4").

 



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