Climate Trends in Southeast South Dakota from 1895 Through 2005

This study used average temperature and precipitation data for the southeast South Dakota climate division from January 1895 through May 2006. The data was collected from the National Climatic Data Center (NCDC). The southeast South Dakota climate division encompasses an area south of a Gann Valley to Flandreau line on the north, a Gann Valley to Bonesteel line on the west, the South Dakota/Nebraska border on the south, and the South Dakota/Minnesota/Iowa borders on the east. 

Ten year running averages of both temperature and precipitation were looked at for annual periods, as well as for winter (December-February), spring (March-May), summer (June-August), and fall (September-November). The 10-year running means were used to capture trends in the climate data while smoothing out the year-to-year fluctuations. Long-term linear trends were also examined. These trends are a best-fit line through the 10-year running mean values from 1905 through 2005. This long-term trend even further reduces the fluctuations in the data allowing the 100 year climate trend signal to be easily seen.

 

 

 

 Annual Trends

Southeast South Dakota has shown a trend toward warmer and wetter conditions in the past 110 years. The linear long-term temperature trend shows warming of about 1 degree Fahrenheit, while the long-term precipitation trend shows a 5 inch per year increase.

 

 

Temperature Trend

Precipitation Trend

+0.6 degrees F

+4.5 inches


The 10-year average annual temperatures were fairly steady from the early 1900s through the late 1920s, followed by rapid warming of around 2 degrees Fahrenheit through the 1930s associated with the Great Depression era. A couple of near record cold years around 1950 brought the 10-year average back close to the long term mean by the early 1950s, which was followed by another rather steady period which lasted into the mid 1980s. Warm periods in the late 1980s and early 2000s have more than offset the cold period of the mid 1990s to produce the current upswing in the 10-year average, which has reached levels warmer than any period seen since the 1930s.

 

  

The 10-year average annual precipitation has show a rather steady and substantial increasing trend since the driest periods of the late 1930s following the Great Depression. Average annual rainfall is around 7 inches more in the mid 2000s than it was around 1940, and has been at or near record levels since 1985.

  

Winter

Southeast South Dakota has seen a significant warming trend for the winter months in the past 110 years, while precipitation has been very consistent through the period. The long-term linear temperature trend shows warming of around 3 degrees Fahrenheit.  

 

Temperature Trend

Precipitation Trend

+2.5 degrees F

-0.1 inches


The ten-year running mean winter temperature shows a gradual warming trend through the first half of the 20th century, followed by steady cooling from around 1950 through 1975. The winter temperatures have then shown a drastic rise of around 6 degrees Fahrenheit in the past 30 years. The current running mean is nearly 24 degrees Fahrenheit, which is 7 degrees warmer than the minimum, which occurred in the late 1910s. Seven of the eight warmest winters on record have occurred in the past 20 years, with only the warmest winter on record, which occurred in 1931, not falling in the past two decades.

 


Ten-year running mean winter precipitation has shown fluctuations of only around 0.50 inch through the last 110 years, despite seasonal extremes that vary by as much as 5 inches.

 

 


Spring

 

The long term trends for southeast South Dakota have shown a gradual warming for the Spring season in the past 110 years, with a much more significant trend for wetter Springs. Average Spring temperatures have warmed 1 to 2 degrees, while precipitation has increased 3 to 4 inches on average for the season.

 

 

 

Temperature Trend

Precipitation Trend

+1.3 degrees F

+3.3 inches


The 10-year running mean temperatures for spring have show wide fluctuations. Averages were fairly steady from around 1900 through 1925, followed by rapid warming of around 2 degrees through the mid 1940s. The next decade saw averages drop by 2 degrees, which was followed by steady warming through the early 1990s, where the 10-year mean reached its peak near 49 degrees. The cool springs of the mid to late 1990s brought the 10-year mean back down 2 to 3 degrees, where is has held through the early 2000s.

 

 

Average spring precipitation was fairly steady from around 1900 through 1920, followed by a slight drop through the early 1930s. An increase of 2 inches in the 10-year mean followed through the early 1940s, where the average spring precipitation then held nearly steady through the mid 1970s. Wet springs in the early 1980s and again in the mid 1990s then pushed the 10-year mean to its record wettest levels, where it has held nearly steady for the past 10 years.

 

 

Summer

The long-term trends of both temperature and precipitation are very steady. Despite extremes in temperatures that range by around 12 degrees, and in precipitation that vary by 14 inches, there is only a very slight trend toward warmer and wetter summers in southeast South Dakota .  

 

Temperature Trend

Precipitation Trend

+0.1 degrees F

+0.5 inches


The only significant departure from normal on the 10-year mean summer temperatures occurred during the Great Depression of the 1930s, where the average rose by nearly 4 degrees for the decade. Cooler summers in the mid to late 1940 brought the 10-year mean back down 3 degrees, where the average has held fairly steady for the past 50 to 60 years.

 

 

The 10-year mean summer precipitation has been fairly consistent. Following a dry period in the 1920s and 1930s where the average dropped by around 2 inches, wet summers in the mid 1940s to early 1950s raised the mean by almost 3 inches. The 10-year mean has since held nearly steady through the early 2000s with the exception of a decrease of 2 inches in the early 1970s, and an increase of just under 2 inches in the early 1980s.

 

 

Fall

For the fall season in southeast South Dakota , cooler and wetter conditions are evident from the long-term trends. Temperatures show about 2 degrees of cooling, while the precipitation is around 1 inch higher. The extremes show a range of nearly 12 degrees in temperature and 10 inches in precipitation. The cool and wet trends were most evident from around 1965 through 1995. 

 

 

Temperature Trend

Precipitation Trend  

-1.4 degrees F

+1.0 inches


The 10-year mean temperatures have shown a slight overall cooling trend in the past 110 years. Temperatures were very steady on average from 1900 through 1960, followed by a slight cooling trend from the mid 1960s to early 1990s. Warmer fall seasons in the past 10 years have brought the 10-year running mean back up close to the warmer levels experienced through the first half of the 20th Century.

 


The 10-year running mean precipitation showed very little variability from 1905 through about 1965. This period has been followed by a gradual trend for wetter falls in the past 40 years, with the average in the early 2000s running about 1 inch wetter than the long-term average and about 2.5 inches wetter than the minimum.

 

 

 


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