June 2021 In Review

Most locations recorded their hottest June in over 30 years (1988). With average temperatures anywhere from 4 to 7 degrees above normal, June 2021 will go down as the 7^th warmest on record at Wheaton, 6^th warmest at Mobridge, the 5^th warmest at Aberdeen and Kennebec, 4^th at Watertown, Pierre and Timber Lake, and the 3^rd at Sisseton. Many locations recorded 10 to 20 days with highs at or above 90 degrees, and up to 5 days at or above 100 (at least one 100 degree June day occurs on average every 2.5 years in Pierre, 5 years in Aberdeen and Mobridge, 12.5 years in Sisseton and 20 years in Watertown). Numerous record daily warm low and high temperatures were set as well, particularly from the 3-10^th, including highs during 5 out of 6 days in Mobridge from the 3^rd through the 8^th.

The heat was in part a testament to just how dry it’s been, both leading up to and also throughout the month. During times of drought, air holds less moisture, and is thus able to heat up faster and to a greater extent. The large-scale weather pattern involved a jet stream that was displaced further north than usual (more typical of July). This meant limited opportunities for quality or widespread storms and rainfall during a time of the year that is typically the wettest on average, climatologically speaking. Aside from fairly isolated pockets, the area ranged from 2 to 3.5 inches below normal for precipitation. This June will go down as the 6^th driest on record in Sisseton, 5^th driest in Aberdeen, 4^th in Pierre, 3^rd in Kennebec, and tied 2^nd at both Watertown and Mobridge. Drought conditions worsened from the 1^st to the 30^th for the majority of central and northeastern South Dakota and west central Minnesota as a result. Fire weather became increasingly concerning as fuels further dried out.

The drought also meant a reduction in severe weather across the area. The NWS office in Aberdeen issued 35 severe thunderstorm warnings across our forecast area this June, and all from the 7-14^th (the average since 1986 is 51). That said, there were a couple events of note. A complex of storms developed and back-built generally from southeastern North Dakota into north central South Dakota from ^{June 7th} into the 8^th. Large hail, damaging winds, a couple tornadoes and flash flooding (10.35” of rain measured near Firesteel) resulted across north central South Dakota. Additionally, a line of intense thunderstorms raced across the area on the night of June 10^th, leading to winds with gusts up to 80 mph. The result was uprooted trees, severe damage to barns and outbuildings, rolled trailers and more, particularly across portions of northern South Dakota.

June 2021's average temperature's departure from normal, courtesy of the Midwestern Regional Climate Center

Calendar day high temperature departures (large number) as well as high temperatures (small top number) and average high temperatures (small bottom number) for Aberdeen, Watertown and Pierre, in that order. 

Number of days this June in the 90s and 100s, and perspective.

Estimated rainfall totals across the region during June, from water.weather.gov. 

Estimated rainfall departures across the region during June, from water.weather.gov. 

Year-to-date information (as of July 1) regarding number of 90+ degree days (horizontal axis) and precipitation totals (vertical axis), as plotted as a large white dot with respect to other years in the database for Aberdeen, Watertown and Pierre in that order. This information for additional cities can be found here. 

A comparison of the US Drought Monitor from the beginning to end of June 2021. 

Looking at the US Drought Monitor another way, we can try to put the area's current drought in context to other droughts in relatively recent history (since 2000) in terms of coverage (not necessarily impact due to timing differences). This graphic shows the percent of the Aberdeen, SD National Weather Service's forecast area under drought and that drought's level of severity. 

Same as above, but across the state of South Dakota. 

Estimated rainfall amounts from June 7-8th. 

Number of severe thunderstorm warnings issued by the NWS office in Aberdeen, SD by month since 1986, highlighting the slow start to the severe weather season across this part of the country. Data courtesy of the Iowa Environmental Mesonet. 

Number of combined severe thunderstorm and tornado warnings issued by the NWS office in Aberdeen, SD by year since 1986, highlighting the slow start to the severe weather season across this part of the country. Data courtesy of the Iowa Environmental Mesonet.