March Madness – a historic month

Published: April 10, 2012

A highly unusual and stagnant warm weather pattern impacted a large area of the United States in March, generally from the Rocky Mountains eastward to the Atlantic seaboard. An area of low pressure remained parked over the Pacific Northwest while an area of high pressure spun clockwise off the Atlantic coast. Gulf of Mexico air was consistently pumped into the heart of the country on southerly wind flow that lasted for days, while the polar jet stream remained locked over Canada, preventing arctic air from spilling into the region.

More than 7,700 daily high temperature records were set during the month and preliminary data indicates it was the warmest March on record for the contiguous United States, surpassing the previous warmest March, in 1910, by 0.5 degrees F. The average March temperature was 51.1°F and was 8.6 degrees above the 20th century average for March.

According to the Midwestern Regional Climate Center, based in Champaign, IL, nine Midwestern states experienced their warmest March ever: Illinois, Indiana, Iowa, Kentucky, Michigan, Minnesota, Missouri, Ohio, and Wisconsin. Only Washington, Oregon, and California experienced cooler than average weather in March.

Preliminary data indicate Missouri's statewide average March temperature was 57.8°F, or 13.1 degrees above normal, ranking it the highest above normal monthly temperature departure for any month in Missouri, since 1895. Monthly double digit departures above normal occur rarely in the Show Me state, having occurred only 5 times since 1895:

Figure 1 shows the magnitude of warmth in Missouri, when compared to Marches in the past, surpassing the previous record, set back in 1910, by nearly 3 degrees. March 2012 also exceeded temperature norms for April in Missouri, averaging 2.7 degrees above the average temperature for April.

Average March temperatures were in the mid 50's across northern Missouri, and upper 50's and lower 60's across central and southern sections. There were many locations across the state where more than half the days experienced high temperatures in the 70's and 80's during the month. Additionally, numerous high maximum and high minimum temperature records were broken. Minimum temperatures remained above freezing in most areas of the state beginning March 11th through the end of the month.

Several significant rainfall events occurred during the month and translated to above normal precipitation for much of the state. The statewide average total was 4.18 inches, or a little less than an inch above normal. Regionally, heaviest amounts fell over west central, southwestern and south central Missouri where 5-7 inches were common. Heaviest amounts were reported in Ozark, Douglas and Newton counties where 9.19, 8.53 and 8.13 inches were observed, respectively. Lighter monthly totals, ranging from 3-5 inches, were common across the rest of the state, with the exception of some northern and eastern border counties where less than 3 inches were observed. Far northeastern counties reported the driest conditions where CoCoRaHS observers in Lewis, Pike and Clark counties reported 1.54, 1.31, and 1.14 inches, respectively, for the month.

Unprecedented warmth and sufficient moisture led to an exceptionally early start to the growing season in March. By the end of month, numerous plants were at growth stages 3-4 weeks ahead of normal and creating significant concern for agricultural and horticultural interests, due to the potential for freezing temperatures in April. Though not widespread, there were also reports of some corn planting occurring in northern and central parts of the state during the last two weeks March.