Written collaboratively by Laura Edwards and Dennis Todey (former South Dakota State Climatologist & SDSU Extension Climate Specialist).
As the warm fall season continues in October, gardens are still producing and fall planting and harvest activities are in full swing. A pattern of warmer than average weather is upon us. Most of the state still has not seen much frost, let alone a hard freeze, which begs the question, when is the latest first freeze we have seen in South Dakota?
To answer this question, we looked at two sources. First, we consulted the Midwest Regional Climate Center’s Vegetation Impact Program. Their website is a great resource for both spring and fall frost (defined at 32° F) and freeze (28° F) information. They have compiled data for the 30-year period of 1980-2010, and the latest fall frost (32F) date is shown in the map below. In South Dakota, those three decades have had the latest first fall frosts occur sometime in October (green shading) with some later dates in November in the south central region.
The second source we considered was the entire historical period for all climate stations in South Dakota, including years before 1980, and in some cases over 120 years of data. The table below shows the latest dates of first fall frost for some selected locations with long historical records. Some of those records occurred in mid-October, in which case it is very possible we could establish new records this year with weather pattern that is in place now. It appears that fall 1963 could have been similar to our current season, with October 27-28 of that year holding several of the latest first fall frost dates across the state. That fall season was also in an El Niño pattern, so we could be on track to match those late first frost dates this year. Average fall frost dates are available on the State Climatologist’s website, demonstrating that a frost in mid to late October would be about a month later than average.
While we await our first fall frost this year, we will continue to enjoy pleasant temperatures for our outdoor activities and fieldwork without our down-filled coats and warmers in our mittens and boots.
Figure 1. Latest occurrence of first fall frost of 32° F during the period of 1980-2010.
Source: Midwest Regional Climate Center’s Vegetation Impact Program
Table 1. Dates of latest occurrence of first fall frosts for selected locations in South Dakota, as of October 7, 2015.
|Brookings 2 NE||10/19/1911||30°|
|Cottonwood 2 E||10/20/1911||28°|
|Interior 3 NE||11/3/1998||29°|
|Source: High Plains Regional Climate Center.|