The terms ‘weather’ and ‘climate’ are often used incorrectly. Weather and climate are not independent. The averages of daily weather are used to monitor climate. Changes in climate lead to changes in weather patterns, including extreme weather events. Climate “normals” are three-decade averages of climatological variables, such as temperature and precipitation. Climate normals provide a historical perspective and help us understand the unusualness for current weather.
This article discusses soil temperature climatology (30-year average) and how 2020 compares to the climate normal for Kansas. To learn more about weather and climatology, please see the publication MF3197-“What is the difference between weather and climate?” at: https://bookstore.ksre.ksu.edu/pubs/MF3197.pdf
2020 Air Temperatures
Last year, late winter and early spring were highlighted with very cold and wet conditions across the region. This led to significant cattle stress impacts, as well as much colder soil temperature records in the east. However, thus far in 2020, a much better balance has occurred. While Kansas has observed colder-than-normal temperatures, they were short lived and were usually countered by warmer-than-normal temperatures the following week (Figure 1). This balance has led to a gradual warm-up in soil temperatures that very closely follows the climatological normal.
Figure 1. State-wide temperature (°F) anomalies by day as measured on the Kansas Mesonet. The 30-year average is represented as the zero line on the y-axis. The red bars (positive values) indicate temperatures were higher than the average. The blue bars (negative values) indicate temperatures were lower than the average. The yearly departure to date for 2020 is 1°F, meaning soil temperatures are approximately 1 degree warmer than the climate normal.
Soil Temperature Climatology
In Kansas, we are fortunate to have 11 Mesonet stations with data going back to the mid-1980s. This includes 2- and 4-inch soil temperatures and the stations are somewhat spread across the state with all 11 still collecting data today. However, there are a few caveats with this dataset: 1) ground cover density and type may have changed over time (dirt vs. grass, etc.) and, 2) only preliminary quality control has been done over the dataset. Regardless, with 30+ years of data, we can still successfully use the trends as a base line. Especially since this much soil data doesn't exist anywhere else in the state. For this quick summary, we focused only on 2-inch soil depth data.
Soil Temperature Summaries by Region
This region was, by far, the wettest this spring. As a result, moist soils have a higher heat capacity and can absorb and hold heat longer than if it were dry. Two-inch soil temperatures ran at, or above, normal for most of the spring (Figure 2). Soil temperatures didn’t impact planting at all - the concern was the wet soils. Folks were unable to get in the field for planting due to excessive soil moisture.
Figure 2. Two-inch soil temperatures this spring at Parsons compared to the Maximum (red), Minimum (blue) and Average (black) over the last 32 years. Source: Kansas Mesonet (mesonet.ksu.edu/agriculture/soiltemp).
Probably the most diverse region, central Kansas saw varying conditions over small distances. Soils here were considerably drier than further east. As a result, they tended to vary more with weather conditions. During periods of abnormal temperatures, soils followed the anomalies but to larger extremes than what occurred in the east. These fluctuations impacted planting the most as the juggling between acceptable soil moisture and precipitation often didn’t cooperate with warm enough conditions.
Figure 3. 2020 two-inch soil temperatures at Hutchinson compared to climatology. Source: Kansas Mesonet data.
Western Kansas unfortunately remained quite dry all winter. Some precipitation events kept the area from falling into worse drought, but at the same time, missed another area that desperately needed moisture. In the south, Garden City (Figure 4) ran well above normal for most of the year to date. With dry soils, little precipitation, and warmer temperatures it makes sense. However, the lack of moisture isn’t ideal for planting despite the above-normal temperatures. These dry soils are also susceptible to drastic swings to below average conditions as observed several times, particularly in April.
Figure 4. 2020 two-inch soil temperature at Garden City compared to climatology. Source: Kansas Mesonet data.
Further north at Colby, it was a bit of a different story. This area saw some abnormally dry drought conditions be eased late winter by several precipitation events. As a result, cooler temperatures prevailed and soil temperatures were slow to warm during these times. In the last month, soils have once again dried out with warmer temperatures, increased evaporation, and plant growth. Therefore, they fluctuate more with the diurnal temperature trends, losing all the afternoon heat gained, and are averaging below the 32-year normal (Figure 5).
Figure 5. 2020 two-inch soil temperatures at Colby compared to climatology. Kansas Mesonet data.
Keep in mind, these are daily averages. Of concern when planting is the risk of minimum temperatures dropping below a particular threshold, usually under 50F. For much of the state, this won’t be a concern as overnight low temperatures will only occasionally drop into the 40s. However, a duration of a few hours isn’t long enough to reduce soil temperatures into concerning levels. The only area that may still have potential is northwest, where daily minimum soil temperatures just eclipsed the 50F mark this week. With warmer-than-normal temperatures in the forecast for the near future, the risk of dropping below 50F is becoming less every day.
Figure 6. Colby 2020 maximum (purple), average (yellow), and minimum (blue) soil temperatures compared to climatology. Source: Kansas Mesonet Data.
Mid-April Cold Period
The most prominent cold period was early- to mid-April where temperatures were below normal for over a week. As a result, soil temperatures fell into the 40s for much of the state. Unfortunately, this was a critical period for planters as corn was beginning to go into the ground. Fortunately, temperatures rebounded quickly with increased sun angle and incoming solar radiation this late in the spring. The duration of below-normal soil temperatures was limited (Figure 7, yellow line in black box) compared to the long duration, and at times record cold conditions observed in 2019 (Figure 7, purple line in dashed black box) and over a month later in the spring. Therefore, any issues were likely isolated and minimal to corn in the ground.
Figure 7. Soil temperature climatology at Ottawa compared to 2020 (yellow), 2019 (purple), and average (gray). Also highlighted are periods of below-average conditions in 2019 (black dashed box) and 2020 (black box).
Soil temperature data: mesonet.ksu.edu/agriculture/soiltemp
The climate data isn’t available online yet but hopefully in the near future. Stay tuned!
Christopher “Chip” Redmond - Weather Data Library Manager
Mary Knapp - Assistant State Climatologist
Ignacio Ciampitti - Crop Production and Cropping Systems Specialist