In the US Midwest, a common rule for timing fall applications of anhydrous ammonia and manure is to apply after soil temperature is below 10^oC (50^oF). Our objective was to evaluate the impact of latitude (37.5 to 43.0 degrees) on soil temperature and accumulation of degree days (0^oC basis) in soil 10-15 cm below the soil surface covered with sod or soybean stubble. We hypothesized that soil degree days accumulate more rapidly (soils cool more slowly) as you move south and that significantly more degree day accumulation occurred in January and February as you move south. We used regression analysis to evaluate 10 years of data from 13 weather stations in four states. The date soil temperatures first reach 10^oC increased 6 days for each degree south. We rejected the hypothesis that soils cooled more slowly as one moves south. The primary difference with latitude was that southern soils accumulated significantly more degree days in January and February. We used our analysis to suggest target soil temperatures and dates for initiating fall nitrogen applications at different latitudes.