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About the MRCC Modified Stress Degree Day Product

Corn SDD Product Description

All plants have an optimum range of temperatures for growth (Hartfield, et al 2001). While it may be obvious that temperatures too cold will inhibit growth (if not damage the plant), temperatures that are too high can cause stress for the plant. Stress Degree-Days (SDD) are a way of tracking how much stress a type of plant has been subjected to within its growing season.

Stress Degree Day Graph
Growth rate response of a hypothetical organism to increasing temperature (Source: Growing degree-day calculation)

There are various ways in which to calculate Stress Degree Days. However, a very simplified approach (i.e., "modified") is to calculate the difference between the daily maximum temperature and the peak optimum temperature for that plant. For example, non-irrigated corn’s optimum maximum temperature is 86°F (Water Stress in Corn). If the daily maximum temperature on a particular day is 92°F, then 6 modified SDD have been accumulated for that day. According to Taylor, "when the SDD (Stress Degree Day based on temperature exceeding 86°F) total exceeds 140 it is tough to find corn yield above trend" (Taylor 2012).

The maps are run daily at approximately 3:00 p.m. CT and show the modified Stress Degree Day accumulations since January 1 to the previous day’s date.

Station Modified SDD Data

If you would like to run Modified Stress Degree Day data for a single station, please visit the cli-MATE (MRCC Application Tools Environment) section of our website. Modified SDD data in both chart plot and tabular data value are available from menu item Station Data > Daily > Degree Data. You may also run plots and tabular data for Heating Degree Days (HDD), Cooling Degree Days (CDD) and Growing Degree Days (GDD) from that cli-MATE product.


Growing degree-day calculation: Agronomy 212 - Grain and Forage Crops, Iowa State University,, Accessed February 2013

Water Stress in Corn: Estimating from Stress Degree Days (SDD), Iowa State University,, Accessed February 2013

Hartfield, J. L., K. J. Boote, B. A. Kimball, L. H. Ziska, R. C. Izarralde, D. Ort, A. M. Thomson, and D. Wolfe, 2011: Climate Impacts on Agriculture: Implications for Crop Productions, Agronomy Journal, 103 (2), 351-370.

Taylor, S. E., 2012:  Water stress in corn:  Estimating from Stress Degree Days (SDD).  Integrated Crop Management News.  Paper 222.