September 2019 In Review

September 2019 featured above normal temperatures on a whole across the area, thanks in large part to much above normal low temperatures. Daily record warm low temperatures in the mid-60s to low 70s were recorded at 16th and/or 17^th at Aberdeen, Watertown, Pierre and/or Mobridge. While the average first 32 degree temperature occurs during the final third of September on average across the area (early October for south central South Dakota), the majority of us avoided it this September. The exception for a few occurred on the morning of the 28^th, when frost was observed across portions of northeastern South Dakota and west central Minnesota in response to generally mid-30 degree temperatures.   

September 2019 was wetter than average across the board, with portions of northeastern and east central South Dakota having recorded the greatest departures from normal (2+ inches). Daily rainfall records were set at Aberdeen, Pierre, Sisseton and Mobridge on the 9^th, 11^th, and/or 12^th. Several locations recorded top-10 wettest Septembers on record: 8^th in Pierre, 6^th in Mobridge, 5^th in Aberdeen, 4^th in Timber Lake, 4^th in Wheaton, and 2^nd in Sisseton (6.65” in 2004). In what was just another wet month in an incredibly wet year, here are some updates for rankings of total year-to-date precipitation through September 30^th: Aberdeen: 25.16” ranks 15^th, Wheaton: 26.44” ranks 10^th, Watertown: 29.42” ranks 3^rd (32.30” in 1977), Timber Lake: 25.34” ranks 3^rd (31.37” in 1915), Pierre: 27.42” ranks 2^nd (28.64” in 1997), Mobridge: 24.15” ranks 2^nd (24.95” in 1915), Sisseton: 29.88” ranks 2^nd (29.99” in 1986), Kennebec: 31.87” ranks 1^st (28.42” in 1915). And here are some updated rankings of total yearly precipitation through Sept 30^th (every additional hundredth of precipitation from now through the remaining 92 days of the calendar year will only add to these rankings/records): Timber Lake: 25.34” ranks 8^th, Mobridge: 24.15” ranks 5^th (26.86” in 1915), Sisseton: 29.88” ranks 5^th (32.30 in 1993), Watertown: 29.42” ranks 4^th (40.04” in 1977), Pierre: 27.42” ranks 4^th (31.85” in 1997), Kennebec: 31.87” ranks 1^st (30.25” in 1915).

September tornadoes in South Dakota aren’t rare, but they aren’t exactly common either. By all measures, September 2019 was active. 6 tornadoes were confirmed on September 9^th across Hamlin, Codington and Day Counties as a broken line of storms in the afternoon and then discrete cells in the evening developed. Find more on this event here: https://www.weather.gov/abr/September9thSevereWeatherSummary. The following night, 4 tornadoes were confirmed across southeastern South Dakota, including 3 in Sioux Falls, along with significant straight-line winds. More on this event here: https://www.weather.gov/fsd/20190910-tornado-siouxfalls. Find perspective on all this in a graphic further down the page.  

September average temperature departures from normal, courtesy of the Midwestern Regional Climate Center

September total precipitation, courtesy of the Midwestern Regional Climate Center

September total precipitation departures from normal, courtesy of the Midwestern Regional Climate Center

September 2019 was very active compared to normal in terms of tornadoes. The stats below feature preliminary data as of October 1st, from the National Centers for Environmental Information's Storm Data

Map of all confirmed September tornadoes since records began in 1950, minus 2019, from the MRCC's Tornado Tracks page