Monthly Overview - December 2019

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Precipitation

Two main storm tracks left Missouri, Illinois and eastern Iowa dry while the Upper Midwest and the Ohio River Valley were wet during the month of December (Figure 1).  Precipitation for the region was 2.51 inches which was 0.30 inches above normal.  Several winter storms impacted the Upper Midwest in December and led to heavy snowfall.  Minnesota, northern Wisconsin and the U.P. of Michigan was impacted the most, with more than twice the normal amount of precipitation for the month (Figure 2).  Minnesota ranked fourth wettest on record (1895-2019), while Michigan and Wisconsin also ranked among the ten wettest Decembers on record (1895-2019).  Several of the cities that broke monthly precipitation records included Brainerd, MN (72 years on record), Iron Mountain, MI (113 years on record) and Superior, WI (107 years on record).  Drier areas across the central Midwest and Missouri led to amounts that were 50-75 percent of normal.  Statewide, Missouri and Illinois had less than 70 percent of normal.  The Dubuque, IA Lock and Dam also reported their driest December on record (82 years on record).
 

Temperature

Widespread warmth enveloped the Midwest during December (Figure 3).  Midwest temperatures were 30.5°F which was 4.6°F above normal.  This ranked among the 20 warmest Decembers on record (1895-2019).  Moderate warmth to start the month gave way to a colder second week of December (Figure 4).  However, second half of December was unseasonably warm, with temperatures exceptionally warm between Christmas Day and New Year’s Eve (Figure 5).  Warmth during the month led to more than 950 daily high maximum and high minimum temperature records across the Midwest (Figure 6).
 

Impacts

While warmer weather limited snowfall in some areas, northern Minnesota and northern Wisconsin had an exceptionally snowy December (Figure 7).  Amounts in these areas were 20-30 inches.  This was more than twice the normal amount in most of these areas (Figure 8).  A significant storm system brought heavy snow on December 1 (Figure 9), while a stalled winter storm on December 28-31 (Figure 10) also brought heavy snow.  December snowfall records were broken in Escanaba, MI (56 years on record) and Detroit Lakes, MN (106 years on record).  During the only cold week of the month, moderate snowfall also impacted the central Midwest (Figure 11). These was the only other areas of the region that had above-normal snowfall.  Most of Iowa, southern Wisconsin, southern Lower Michigan, and eastern Ohio had less than half the normal amount, with some areas having less than 25 percent of normal.
 

-BJP-