Around this time of year, South Dakotans are expecting a hard frost to bring a conclusion to the growing season. Late September and early October are the average fall frost dates for most areas of the state, particularly in the Eastern Regions. In reviewing the last 30 years of climate data, all areas of the state report a frost before the end of October 90 percent of the time. That leaves a few outliers of extremely late frosts that occur in November.
2016 Frost Dates
Last year, many Southern and Southeastern areas had near-record late frosts, with the latest fall frost in at least 30 years. Some locations did not record a minimum temperature below 32 degrees F until the second week in November. Last year was truly exceptional in this regard, and the long growing season may have been a contributor to the 2017 drought. It is thought that the extended growing season allowed winter wheat in particular to deplete soil moisture that is typically reserved through the winter season. This soil moisture can then made available after spring thaw for new vegetation growth.
Given the climate outlook for warmer temperatures more likely than not to return to the Region in October, it is possible that most of the state will again have a late frost. It is too hard to tell if growers and gardeners will be harvesting into November as they did last year, but almost certainly the frost will be later than the 30-year average.
Corn is slow to mature and dry down this year. As of September 25, only 32 percent of the corn crop is mature, according to the USDA NASS survey. The five year average is 57 percent mature for this time of year. Soybeans were just 4 percent harvested, down from the five year average of 17 percent. The potential for a late frost will increase the chances for these crops to reach maturity and dry down in the field before harvesting occurs.