Missouri 2017 Growing Season Climate Summary

Pat Guinan
MU Extension/State Climatologist
Commercial Agriculture Program

November 28, 2017

Missouri’s growing season began with planting opportunities during the first few weeks of April, but widespread, significant rain events during the last week halted fieldwork activity and concerns for flooded cropland and replanting emerged. Exceptional wetness impacted the state by the end of April with a statewide average monthly total of 9.46 inches, more than twice the normal monthly total. It was the wettest April in 123 years of climate records.

A historic rain and flood event impacted the southern half of Missouri during the last weekend of April when many areas received 4-10 inches of rain on April 29-30. Rain gauges and radar estimates indicate several counties in far southern Missouri received 8-10 inches during the 2-day period. Numerous rivers and streams overflowed their banks and thousands of bottomland acres were inundated.

Despite unprecedented wetness, corn planting was 67% complete by the end of the April, 11 percentage points ahead of the 5-year average, according to the Missouri Agricultural Statistics Service. Stock water supplies were reported mostly adequate (65%), as well as hay supplies and other roughages (83%). Nearly two-thirds of the pastures were in good condition and 62% of the topsoil moisture supplies were reported surplus statewide.

Alternating cool and warm periods occurred in May with coldest temperatures during the first week, warmest conditions during mid-month and near average temperatures toward the end of the month. Precipitation data indicated a statewide average May total of 5.97 inches, nearly 1-inch above normal. Record April rainfall, in combination with above average May precipitation, translated to the wettest spring (Mar-Apr-May) in more than 40 years, and 4th wettest spring on record for the Show Me State.

May rainfall was variable across the state with heaviest totals observed across the southeastern half of Missouri, where 5-8 inches were common. Some locations across southern Missouri reported more than 10-inches of rain for the month. Drier, below normal rainfall occurred across much of northern Missouri where some locations observed less than 2-inches for the month, less than 50% their monthly average.

According to the Missouri Agricultural Statistics Service, as of May 28, 99% of Missouri was reporting adequate to surplus topsoil moisture conditions, and 98% of the state reported adequate to surplus subsoil moisture conditions. Statewide pasture conditions were reported 75% good to excellent. Nearly all the corn was planted by the end of the month (97%) and 53% of the corn was reported in good to excellent condition. Just over half of the soybean had been planted by the end of May (54%).

June weather conditions shifted notably in Missouri with a pattern change mid-month from warm and dry to cool and wet. The statewide monthly average temperature was 73.4°F, or 0.4°F above normal.

June rainfall was variable across the state with heaviest amounts reported across northern and western Missouri, where 4-7 inches were common. Lightest monthly totals, less than 4-inches, were typical over east central, south central and southeastern sections. Pockets of dryness, where less than 2-inches inches fell for the month, were located south and southwest of St. Louis, generally centered in Crawford and Washington counties. Highest rainfall totals were found in north central and northwestern Missouri where some counties reported more than 10-inches for the month.

Extreme rain events impacted parts of northern and western Missouri toward the end of the June. The first event occurred during the evening and early morning hours of June 28-29 when severe thunderstorms developed from Atchison to Mercer counties. The storms initially brought reports of large hail, straight-line wind damage and a few tornadoes. Crop damage from wind and hail were also reported. As the evening progressed extremely intense rainfall occurred over portions of northwestern Missouri. There was major flash flooding with numerous reports of road closures, flooded residences, and thousands of acres of submerged cropland. Radar rainfall estimates and rain gauge reports indicated more then 10-inches had fallen over parts of Nodaway, Worth, Gentry and Harrison counties.

Another wave of storms impacted parts of north central and west central Missouri later in the day on June 29 and into the morning of the 30th. Portions of Macon, Linn, Livingston, Chariton, Carroll, Saline, Lafayette, Clinton and Caldwell counties reported more than 5-inches. Heaviest rain gauge reports were from Saline and Chariton counties.

According to the Missouri Agricultural Statistics Service, for the week ending July 2, only 12% and 11% of the topsoil and subsoil moisture supplies, respectively, were in short to very short condition in the state. Corn was rated mostly good to excellent at 67%, and soy conditions were mostly good to excellent at 62%. Pasture conditions were in mostly good to excellent condition at 69%. The majority of hay and stock water supplies were adequate to surplus at 96%.

The overall July weather in Missouri was hotter and drier than normal, but there was notable variability in areas of the state. The statewide average temperature for the month was 78.8°F, or 1.5 degrees above normal. Driest parts of the state were over east central and north central sections. Some of the hottest temperatures experienced in five years occurred during a 5-day heat wave from July 18-22. High heat indices accompanied the hot weather and made it uncomfortable for outdoor activity.

July rainfall was highly variable across the state, but the statewide average total was 3.37 inches, or 0.87 inches below normal. Wettest conditions, where more than 4-inches were reported, were found over portions of northwestern, west central, central and southeastern Missouri. Driest locations, where less than 2-inches were observed, occurred in a corridor across northern Missouri, from St. Joseph to Hannibal. Another corridor of droughty conditions extended from St. Louis southwestward to south central Missouri, and westward to near Joplin. Many lawns and pastures in this region were in poor to very poor condition.

On July 12-13, a flash flood event dropped more than five inches over portions of northwestern Missouri, from Harrison to Grundy counties. There were localized reports of more than 8-inches. Another flash flood event impacted west central Missouri on July 26-27, with several locations reporting 4-7 inches, and localized reports of more than 8-inches.

According to the Missouri Agricultural Statistics Service report from July 30, 59% of the state reported topsoil moisture supplies in adequate condition with 35% of the state reporting topsoil moisture in short condition. Statewide subsoil condition was reported 68% adequate. Corn, soybean and pasture conditions were reported at 61%, 65%, and 50% in good to excellent condition, respectively. The majority of hay and stock water supplies were adequate to surplus.

A significant pattern change to cooler weather began during the last week of July and persisted through much of August. The statewide average temperature for August was 72.0°F, or 4.1 degrees below normal. It was Missouri’s 7th coolest August on record and coolest August since 2004.

August rainfall was variable, but the statewide average was 5.10 inches, or 1.47 inches above normal. Notable precipitation variability for the month translated to some areas experiencing drier than normal conditions. Some counties in east central and southeastern Missouri reported less than 2-inches for the month, whereas more than 10-inches were observed over portions of west central and southwestern Missouri.

An extreme rain event impacted portions of west central and south central Missouri on Aug 5-6 when 4-8.5 inches fell over a corridor extending from Jackson to Pulaski Counties. Another extreme event impacted west central Missouri on Aug 21-22 with 5-8 inches reported from Platte and Clay counties southward through Jackson and Cass counties. Parts of west central Missouri experienced 3 major flood events since the beginning of June.

According to the Missouri Agricultural Statistics Service report for the week ending August 27, 2017, 76% of the state reported topsoil moisture supplies in adequate to surplus condition. Similarly, 74% of the subsoil moisture supplies were in adequate to surplus condition. Corn was reported 62% in good to excellent condition compared to 76% at the same time last year. Soybean was 64% in good to excellent condition compared to 73% last year. Pastures were rated at 61% in good to excellent condition compared to 67% last year. Hay and other roughages were 95% adequate to surplus, similar to last year.

The summer of 2017 was characterized with highly variable rainfall across the Show Me State, ranging from extreme wetness to drought. Some counties in west central Missouri received more than 25-inches for the summer (Jun-Aug). Alternatively, some of the lowest rainfall totals were found across eastern Missouri, especially in an area south and southwest of St. Louis, where less than 6-inches were observed for the entire summer period.

Above normal temperatures dominated the Show Me State during September, especially after the first week of the month when a ridge of high pressure, parked over the western United States, shifted eastward into the middle part of the country. An early autumn heat wave brought the warmest weather for the month, with many locations reporting several days of high temperatures in the 90's. The statewide average monthly temperature was 70.3°F, or 2.7 degrees above normal.

Rain events were few, light and sporadic during September with a statewide monthly average of 0.98 inches, more than 3-inches below normal. It was the 5th driest September on record for Missouri, and driest September since 1956. Driest weather occurred over northeastern sections and in a 60-mile wide corridor extending from southwest of St. Louis to Branson. Another corridor of low rainfall totals extended from south of West Plains to Poplar Bluff, northeastward to Cape Girardeau. Radar rainfall estimates from many locations in the aforementioned areas were less than 0.50" for September. Abnormally dry to moderate drought conditions were impacting much of northern, eastern and southern Missouri by the end of September.

According to the Missouri Agricultural Statistics Service, as of October 1, 67% of the corn and 66% of the soybean crop was reported in good to excellent condition. The majority of hay and roughages were adequate (76%) to surplus (15%), while 81% of the stock water supplies were adequate. Corn harvest was advancing behind average at 44% compared to the 5-year average of 53%. Only 39% of the pastures were reported in good to excellent condition. More than half of the topsoil moisture conditions in the state were short (38%) to very short (21%). The majority of subsoil moisture conditions were also reported short (39%) to very short (15%).

Anomalous autumn warmth persisted through much of October with temperatures averaging 5-7 degrees above normal for the first 3 weeks of the month. A wetter pattern emerged, especially across northern, central and southwestern sections, and mitigated dryness concerns, with the exception of southeastern Missouri, where dry conditions persisted.

Wetter October weather limited opportunities for crop dry-down, harvest and other fieldwork activities. According to the Missouri Agricultural Statistics Service, for the week ending October 22, corn and soybean harvest was 69% and 45% complete, respectively; 12 percentage points behind the 5-year average for corn and 3 percentage points behind for soybean. The majority of topsoil and subsoil moisture conditions were reported adequate at 69% and 66%, respectively. Hay supplies and stock water supplies were also mostly adequate at 78% and 79%, respectively.

A northwesterly upper air flow pattern brought Canadian air masses into the region during the last week of October and resulted in cooler, below normal temperatures. The growing season effectively came to an end when widespread freezing temperatures impacted much of the state on October 28-29. Median spring and autumn dates for specific freeze thresholds in Missouri can be found at http://ipm.missouri.edu/FrostFreezeGuide