December 31, 1967: Weather During the Icebowl

Green Bay - Ice Bowl Weather Facts

• The coldest and longest cold stretch (nine days) during the 1967-1968 winter season began the day of the Ice Bowl. Seven of nine days during that stretch did not exceed 0°F.
• The winter in which the Ice Bowl was played (1967-1968) ranked 2nd all-time for the least snowiest (20.6 inches). The record is 19.2 inches during the winter of 1960-1961.
• The Ice Bowl ranked 1st all-time for the lowest average temperature for any December 31 in Green Bay: -6.5°F for the day.
• The Ice Bowl ranked 1st all-time for the lowest minimum temperature for any December 31 in Green Bay: -19°F reached just before midnight that evening.
• The Ice Bowl ranked 5th all-time for the lowest maximum temperature for any December 31 in Green Bay: +6°F reached at midnight early that morning.

The Weather Leading Up to the Ice Bowl

The overall weather pattern during the month of December 1967 underwent a rather dramatic "second half adjustment." The upper level flow during the first half of the month was characterized by a "split flow" regime. The west-to-east northern stream over Canada essentially blocked the Arctic air from moving southward into the United States (figure on left, below). However, during the second half of the month, the upper air pattern changed dramatically such that by the end of December 1967, a large polar vortex had become established over Hudson Bay with a large and deep trough centered right over the central United States (figure on right, below). This pattern change allowed the Arctic air that was building up in Canada earlier in the month to spill south into the United States by the end of the month.

500 mb (~ 18000 ft) chart on December 16, 1967. Click image for larger view.	500 mb (~ 18000 ft) chart on December 28, 1967. Click image for larger view.

The graph below shows the trend in the daily average temperature during the month of December 1967. 

Daily average temperatures in December 1967. Click image for larger view.

The Weather the Day of the Ice Bowl

The weather the day before the Ice Bowl was relatively tranquil with a high of 20°F. However, later that evening shortly before midnight, an Arctic front swept across the state ushering bitter cold air into the state. The temperature fell nearly 30 degrees during the 12 hour period ending at 9 AM the morning of the Ice Bowl. By 9 AM Sunday, December 31, 1967, the temperature plummeted to minus 16°F with wind chill values falling to 38 below zero. During the game, actual temperatures ranged from -12°F to -14°F with wind chills (based on the new wind chill index) ranging from 33 to 37 below zero, making it the coldest game in NFL history.

Surface weather chart on December 31, 1967. Click image for larger view.	Three-hourly weather on December 31, 1967. Click image for larger view.

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