May 2018 was a 180-degree turn from April. South Dakota had its second coldest April on record, to something close to the tenth warmest May on record. As we are in early June, it appears as if the heat will continue.
Western South Dakota had temperatures about two to six degrees above average for the last month. Eastern South Dakota recorded temperatures that were about six to ten degrees above average. Many locations ranked in their top ten warmest Mays on record. Aberdeen likely reached the highest, as preliminary data suggest it was the third warmest May on record, behind 1934 and 1977. Watertown recorded its seventh warmest May. Both locations have climate records that date to 1893.
Most of the state recorded their last 32F freezing temperature in late April, likely around the time the last snowstorm crossed the region. This is about two weeks earlier than the median date.
May 2018 was also quite dry across much of the eastern half of the state. Aberdeen was among the driest locations, measuring only 0.52 inches of rain, 2.59 inches below average. Drought conditions expanded in the northeast, which was in moderate drought on the U.S. Drought Monitor on May 31. For some, this was welcome news as row crop planting progressed quickly after a slow start in April. Much of the eastern rivers were in minor to moderate flood stage to start the month of May, and by late May had receded to near normal flows.
The warm and dry weather in the eastern counties also provided ideal conditions for rapid emergence and growth for field crops. Unfortunately, it was also favorable conditions for weed growth as well. Breezy and windy conditions limited some pre-emerge herbicide application. Spotty rainfall created some challenges for effectiveness of some herbicides, as some areas did not receive enough moisture to activate well enough for good control.
Western South Dakota had some very wet areas in the Black Hills and southwest. Some areas in Fall River and Custer county measured five to eight inches of rainfall for the month.
Elsewhere in the west, rainfall was spotty and did not provide sufficient moisture to remove drought concerns. May moisture is critical for grass, pasture and forage production. Following a drought year, spring precipitation is even more important, and it appears likely that forage production will be below average again for west central and some northwestern areas.
The climate outlook for June 2018 shows increased chances of warmer than average temperatures. This is certainly true for the first two weeks of the month, as there is very high likelihood of warm temperatures to continue across the Northern Plains.
The rainfall outlook for June is less certain. The NOAA Climate Prediction Center is projecting slightly increased chance for wetter conditions in the Red River Valley, including areas of eastern North Dakota, northwest Minnesota, and northeastern South Dakota. The remainder of the state has equal chances of wetter, drier or near average rainfall in the month ahead.
As we enter into our wettest month of the year, rainfall will be critical across the state to prevent further drought expansion, and to maintain good crop conditions and water supply for livestock.
Figure 1. June 2018 precipitation outlook. Northeastern South Dakota is slightly favored for wetter than average conditions. Elsewhere in the state, there are equal chances of wetter, drier and near average rainfall for June. Source: NOAA Climate Prediction Center.