On September 30, NOAA’s Climate Prediction Center released an update to the October climate outlook. For the Northern Plains, there are some substantial changes to the previous outlook that was issued a couple of weeks ago.
There is much more certainty that cold air will hold over the region in early October. For at least the first couple weeks of the month, there is very high likelihood that colder than average temperatures will affect much of the western and Northern Plains states. Some forecasts show 20 to 30 degrees F below average over the Native American/Columbus Day weekend. With temperatures this cold, the month overall is likely to end colder than average.
Despite the cooler air moving into the area from Canada, some areas of the state have still not had a frost or hard freeze. As of this writing, only the northwest, Black Hills, north central and northeastern areas have reported sub-freezing temperatures. A hard freeze would punctuate the end of the growing season for weeds, disease and insects in our crops and gardens. Early October is the average frost date for much of central and southern South Dakota, so it would not be unusual to have a frost occur soon.
An active weather pattern will also be crossing South Dakota, at least in the first couple of weeks of the month. There is some confidence that the month overall will end wetter than average due to the soggy start. Part of this moisture will be remnants of Tropical Storm Rosa, and part of the moisture will come from fronts or some shortwaves moving across the region. Several days of rain or snow are expected in the next couple of weeks.
Impacts on Cropping Systems
This outlook for wetter and cooler conditions will likely cause some delays in corn and soybean harvest, particularly in the southeast. These conditions are not favorable for natural air drying grain in the field, nor for heavy farm machinery to move through wet soils. This area has struggled with excess moisture for much of the year, as only two months so far in 2018 have had below average rainfall. Growers will need to utilize the short windows of warm and dry weather to harvest and complete fall field work. Much of the winter wheat is planted in central South Dakota. The moisture will encourage germination and emergence before frost comes.
Figure 1. October 2018 precipitation outlook, updated 30 September 2018. The forecast favors wetter than average conditions in South Dakota for the month overall.