August 2020 Weather and Its Impacts on Missouri

Pat Guinan
State Climatologist
University of Missouri Extension

Seasonably cool August temperatures impacted Missouri with preliminary data indicating a statewide average temperature of 74.2°F, or 1.9 below the long-term average, Figure 1. It was coolest August since 2017. Near to below normal temperatures occurred during the first three weeks of August followed by warmer conditions in the final 10-days, including a few days with high temperatures in the lower and mid-90s, Figure 2. It was the third cooler than average month for the year, Figure 3.

Daily summer temperatures this year reflected the overall trend for the past few decades, with no prolonged periods of extreme high temperatures. Preliminary mean summer temperature data (Jun-Jul-Aug) indicate slightly above normal conditions this year, Figure 4. The statewide average summer temperature was 76.1°F, 0.5 above the long-term average. Summer weather patterns over the past several decades indicate little change in maximum temperature trends whereas minimum summer temperatures have been warming, Figures 5 and 6. This phenomenon is primarily due to above average summer dew point temperatures in Missouri, Figure 7, which act to suppress maximum air temperature and elevate minimum air temperature.

Drier than average weather impacted Missouri in August with preliminary data indicating a statewide average of 2.89 inches, 0.81 inches below the long-term average. It was the first drier than average August since 2012, Figure 8, and third below average month for the year, Figure 9.

Typical of the summer season, August rainfall was highly variable, ranging from less than 0.25 inches to nearly 1-foot. Radar estimates indicated pockets of more than 5-inches in parts of the state and driest areas located in some far northern counties and southwestern sections, Figure 10. Remnants of Hurricane Laura impacted southeastern Missouri on August 28. Some of the lightest and heaviest August rain gauge reports are listed in Table 1.

According to the U.S. Drought Monitor map, for the week of August 25, 2020, abnormally dry conditions to severe drought was impacting parts of Missouri, Figure 11. Impacts were accumulating, with crop stress, burned-up pastures and decreasing water supplies reported in parts of southwestern Missouri where dry conditions have been ongoing since early June.

Missouri High and Low Rainfall Extremes for August 2020*
Station Name* County
Rainfall (in)
HeaviestHermann 3.0S Gasconade 11.72
 Poplar Bluff 4.2NW Butler 10.01
 Ellsinore 4.8WNW Carter 9.82
 New Haven 2.3S Franklin 8.26
 Williamsville Wayne 8.04
LightestBurlington JunctionNodaway 0.19
 Grant City 0.5NE Worth 0.20
 Unionville Putnam 0.21
 Lancaster 0.2SE Schuyler 0.33
 Linneus 2.5ESE Linn 0.43
*Rain gauges are from the NWS Cooperative Network or CoCoRaHS Network
Table 1.

According to the Missouri Agricultural Statistics Service report for the week ending August 31, 2020, 64% of the state reported topsoil moisture supplies in adequate condition with 1% surplus, whereas 31% of Missouri reported short topsoil moisture supply and 4% very short. Subsoil moisture supplies were reported 69% adequate and 0% in surplus condition compared to 29% of the state reporting subsoil moisture supplies short and 2% very short. Corn was reported 77% in good to excellent condition compared to 38% last year. Soybean was reported 75% in good to excellent condition compared to 46% last year. Pastures were rated at 55% in good to excellent condition compared to 70% last year. Hay and other roughages were 87% adequate to surplus compared to 84% last year. Stock water supplies were 91% adequate and 9% short.

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Missouri Average August Temperature 1895-2020*

Figure 1.

Columbia, MO August Daily Max/Min Temp Normal vs 2020

Figure 2.

Missouri Monthly Temperature Departure from Average* Jan 2019 - Aug 2020**

Figure 3.

Missouri Average Summer Temp

Figure 4.

Missouri Average Summer Max Temp

Figure 5.

Missouri Average Summer Min Temp

Figure 6.

Average Summer Dew Point Temp Columbia, MO

Figure 7.

Missouri Average August Precip 1895-2020*

Figure 8.

Missouri Monthly Precip Departure from Average: Jan - Aug 2020**

Figure 9.

Radar Estimated Rainfall August 2020

Figure 10.

Drought Monitor Missouri August 25, 2020

Figure 11.

Average Temp Missouri August 2020

Average Temp Departure Missouri August 2020

Accumulated Precip Missouri August 2020

Accumulated Precip Departure Missouri August 2020

Source: Pat Guinan, 573-882-5908