Missouri Climate Summary for 2011

Pat Guinan
State Climatologist
Commercial Agriculture/University of Missouri Extension

Missouri weather in 2011 was anything but uneventful. From blizzards and tornadoes to floods, heat waves and drought, it was a year of extremes. There were 3 major disaster declarations for Missouri in 2011, which amounts to 20 declarations in the past 6 years. Only Oklahoma has had more over the same time span, with a total of 25 state disaster declarations.

The year started out cold and snowy and persisted through the first half of February. The most notable winter event, known as the Groundhog Day Blizzard, occurred on February 1-2 and dropped 15-23 inches of snow over a large part of the state. Several locations established all time 24-hour snowfall totals and there were several reports of thundersnow from Joplin through portions of central and northeastern Missouri. Snowfall rates approached or exceeded 2 inches per hour in many locations and wind gusts in excess of 35 mph occurred during the event, creating whiteout conditions and road closures. Warrensburg, MO officially reported 23 inches of snow.

Portions of I-44 were closed in southwestern Missouri and an unprecedented closing of Interstate 70 occurred from Kansas City to St. Louis. Additionally, the University of Missouri-Columbia campus was closed for 3 consecutive days. The heavy snow posed stress to cattle and newborn calves and figures from the Missouri Department of Transportation indicated clean up costs approached $8 million.

Wet and cool conditions emerged at the start of spring and, by the end of April, planting opportunities had come to a halt across the state. According to the Missouri Agricultural Statistics Service, spring tillage at the end of April was 8 days behind average and less than a third of the corn crop had been planted. It was the 5th wettest April on record for the state and the wettest ever for southeastern Missouri. More than a foot of rain fell across southeastern sections and locations in Shannon, Carter, Butler and Cape Girardeau counties reported more than 20 inches of rain for the month. Extensive flooding occurred across southeastern Missouri and replanting was necessary for numerous flooded fields across the state. Some record crests were established along the Mississippi River, south of Cape Girardeau to New Orleans, and hundreds of thousands of bottomland acres were flooded.

Another unusual April event was a strong tornado that struck the St. Louis area on Good Friday, April 22nd. An EF-4 tornado tracked continuously for 22 miles impacting several communities including Lambert St. Louis International Airport. The Airport incurred substantial damage and was closed for the first time since the Blizzard of January 1982. It was the strongest tornado to impact St. Louis County in 44 years.

May had below normal temperatures and above normal precipitation, but much of the month was dominated by highly contrasting air masses, leading to periods of much warmer than normal and much cooler than normal weather. The statewide average precipitation total for the month was just over 6 inches, or 1- inch above normal.

Another extreme event, in the form of a historic tornado, occurred during the late afternoon of Sunday, May 22. All the ingredients fell into place for a deadly tornado that left an indelible mark on Joplin, MO, a community of 50,000 people. The EF-5 tornado claimed 161 lives and ranks as the deadliest single tornado on record for the state of Missouri, as well as Missouri's costliest natural disaster, more than $2 billion. For the United States, the Joplin tornado ranks as the 7th deadliest on record and the deadliest since 1947. Estimates indicate that nearly 30% of Joplin was damaged or destroyed.

An unusually warm air mass established itself over Missouri during the first ten days of June with oppressive heat impacting the state and several high temperature records broken. Temperatures averaged 8-10 degrees above normal during the period and it was the hottest June 1-10 period since 1934. A pattern change led to a more seasonable and below normal temperature regime for the remainder of June and was a welcome change for many. Springfield, Joplin and West Plains had their 6th, 4th and 4th hottest June on record, respectively.

Precipitation was highly variable during June with a sharp gradient extending from northeastern through southwestern Missouri. Amounts increased northeast of a St. Joseph to Cape Girardeau line, from 4.5 inches to more than 12 inches. Totals decreased southwest of this line, from 4.5 inches to less than 1-inch. Some of the highest June rainfall totals occurred in Lewis and Clark counties where amounts exceeded 15 inches. Some of the driest communities were in Christian and Greene counties where less than 1-inch was reported.

As summer progressed, major flooding continued along the Missouri River, due to record water release from upstream reservoirs in Montana and the Dakotas. These record releases translated to major flooding downstream to St. Joseph, MO and moderate flooding along the Missouri River from Kansas City to Jefferson City, MO. Thousands of acres of cropland were flooded in northwestern Missouri where overtopped levees and levy breeches worsened the situation. Atchison and Holt counties, in the northwest corner of the state, experienced numerous impacts with flooded residences, closed roads and inundated cropland.

The mercury climbed higher in July as a ridge of high pressure over the southern Plains intensified and expanded northeastward into Missouri. Hot and dry conditions spread across Missouri and had adverse impacts on people, animals and vegetation. The average statewide temperature for the month was 83°F, slightly more than 5 degrees above normal, and the hottest month since July 1980. Another feature of the prolonged heat wave was high minimum temperatures. The average July minimum temperature for most areas of Missouri was between 72-74°F, which is five to six degrees above normal.

Most areas of the state reported dry conditions in July and precipitation observations indicated a statewide monthly average of 2.43 inches, more than 1.5 inches below normal. The majority of events were scattered and highly localized, but there were a few instances of significant rainfall. Some especially dry pockets were found in parts of northeast, west central, southwest and southeast Missouri where less than 0.75 inches were reported for the month.

Hardest hit by lack of precipitation and extreme heat was southwestern Missouri, where a full- fledged drought had emerged. According to the Missouri Agricultural Statistics Service, 84% of the corn and 91% of the soybean crop was in very poor condition by the end of the July. Complete crop failures were reported in southwestern Missouri and burned up pastures were forcing livestock producers to feed hay in some areas.

Above normal temperatures persisted into August, wrapping up another hot summer for the Show Me State. June through August temperatures were slightly under 79°F, and rank the summer of 2011 as the 7th hottest on record, 0.2°F warmer than the summer of 2010. Precipitation events were more numerous, and heavier, across parts of Missouri during August than the previous month, bringing some relief to the state. Observations indicate a statewide average of nearly 4.0 inches, which is above the 30-year normal. Regionally, totals across the southwestern half of Missouri were near to above normal and averaged between 3-6 inches, whereas rainfall totals were below normal, less than 3-inches, across the northeastern half of the state.

A weather pattern change in early September brought seasonably cool conditions to the state. Monthly average temperatures ranged 2.5 to 3.5 degrees below normal for many locations. A fairly active and progressive weather pattern dominated as several frontal boundaries swept through the state and brought periods of precipitation. Most rain events, however, were not widespread, nor heavy, and preliminary data indicated an average statewide total of nearly 2.60 inches, more than 1-inch below normal for the month.

According to the Missouri Agricultural Statistics Service, the generally dry weather during September hastened fieldwork activity over much of the state and allowed producers to harvest nearly two thirds of the corn by the end of the month. Soybean harvest was going at a normal pace and nearly 10% was harvested by the end of the month. Nearly 50% of the pastures were in poor to very poor condition at the end of the September due to lingering effects of summer heat and drought that impacted much of state, especially across west central, southwestern and northeastern sections. There were numerous reports of farmers feeding hay as well as hauling water due to dry ponds, springs and creeks. Pasture deterioration was also noted across north central and northwestern sections due to unusually dry September weather.

Dry conditions continued into October with temperatures averaging near normal across southern Missouri and one to two degrees above normal across northern and central sections. All locations reported below normal rainfall with some unusually dry conditions in northwestern and west central Missouri. Several counties in northwest and west central Missouri received less than 0.25 inches for the month and a couple precipitation observers in Atchison and Harrison counties reported no measurable rainfall for October. Official precipitation reports indicate it was the driest September-October period in 55 years across northwestern Missouri, and the third driest on record.

A welcome mild and wet weather pattern emerged in November and remained intact through the end of the year. Temperatures during November were seasonable to above normal on most days, reaching the 50's and 60's on many occasions. Some areas managed to avoid a hard freeze as evidenced by roses still blooming and greener than normal lawns and pastures by the end of the month. Much of the state received 4-6 inches of precipitation, but lighter amounts were reported across portions of northwestern Missouri where 3.5-4.0 inches were typical. Heaviest precipitation occurred in far southeastern sections, especially in the Bootheel region, where 9-11 inches were common. It was the wettest November for the Bootheel since 1973, and the 3rd wettest on record. Additionally, the Bootheel witnessed a rare November snow event that blanketed the region with 2-6 inches of snow on the 28th and 29th. It was the heaviest November snow event for the Bootheel in 36 years.

Meteorological winter got off to a mild and wet start across the Show Me State with temperatures averaging 4 degrees above normal and precipitation around 1-inch above normal for the month of December. Preliminary data indicate the statewide average temperature was 37°F with regional average temperatures ranging from 34-36°F across northern Missouri, 37-39°F in central sections and 39-42°F across the south.

December precipitation was variable, but, with the exception of extreme southwestern Missouri, was above normal statewide, ranging from 2-3 inches across northern Missouri, 3-4 inches across central and southwestern sections, and 4-6 falling southeast of a line from St. Genevieve to Branson. Heaviest December totals were confined to the Missouri Bootheel where amounts ranged between 6-8 inches. It was the wettest November-December period in the Bootheel since 1957. Snow events were infrequent and light during the month. Some locations had yet to receive any measureable snow for the season.

The numerous rain events, in combination with unfrozen soils, acted to help recharge the soil profile and mitigate lingering drought affecting portions of northern and western Missouri. Several benefits were derived from the mild weather regime including reductions in heating demand for housing, businesses and farm facilities. Additionally, transportation costs associated with snow plowing, salting, and sanding were minimal and hazardous travel conditions were sparse. Construction activities flourished and digging opportunities were unhindered due to no frost line in the soil. Exposed livestock also benefited from the mild weather as the year came to an end.