Midwest Overview - December 2012
Warm Month Brings an End to a Warm Year
December got off to a very warm start and despite cooling late in the month, monthly temperatures were only moderated slightly (Indianapolis for example, Figure 1). Temperatures ranged from near normal in northwest Minnesota to as much as 6° to 7°F above normal in large parts of Illinois and Indiana (Figure 2). December daily temperature records were dominated by record highs (over 800 for the month compared to just 5 record lows) especially from the 2nd to 4th and 15th to 17th (Figure 3).
Annual temperatures for 2012 were among the warmest on record. January to December temperatures averaged from 1° to 5°F above normal across the Midwest (Figure 4). The nine-state region as a whole experienced its warmest year dating back to 1895 with a temperature of 52.1°F (based on preliminary estimates) topping the old record of 51.9 °F in 1931. Each of the nine states ranked among the top 3 warmest in the same time period. Missouri set a new statewide record (58.5°F vs. 57.6°F in 1938) in 2012 while Illinois and Ohio tied their existing record. Many cities across the Midwest also set new annual temperature records as shown in the table below.
Snow Spreads South in December
Following a fall with relatively low snow totals, December brought some significant snows (Figure 5). Early in the month on the 9th and 10th, heavy snows fell in southern Minnesota and west central Wisconsin (Figure 6). Totals ranged from 6" to 13" across those areas. December 19th and 20th saw blizzard conditions extend from Iowa to northern Michigan. Snowfall totals ranged up to 15" in parts of southern Wisconsin (Figure 7). On the 26th, another round of blizzard conditions extended from southeast Missouri to Lake Erie. Another storm followed a similar path just days later pushing snowfall totals over a foot in many locations along the path of the storms (Figure 8).
December precipitation (Figure 9) totals ranged from well below normal (less than 50% of normal) in northwest Minnesota, western Missouri, and a small area in Upper Michigan. Areas with twice their normal precipitation for the month were located in southwest Minnesota and southeast Ohio.
Annual precipitation values were mostly below normal in 2012 across the region (Figure 10). Some areas along the northern and eastern edges of the Midwest were slightly above normal but large areas of Missouri, Iowa, and Illinois received between 50% and 75% of normal precipitation for the year. Drought conditions were widespread in summer but the eastern parts of the region improved in the fall while conditions deteriorated to the north and west as the year progressed