Authors: Romulo Lollato, Mary Knapp, Chip Redmond, Erick DeWolf

The mornings of May 1st and 2nd brought cold temperatures to the northwest region of Kansas. Minimum temperatures during the morning of May 2nd were lower than 28°F in Cheyenne, Sherman, and Wallace counties (Figure 1).

Figure 1. Minimum temperatures measured in the morning of May 2nd.

The morning of May 1st was not as cold, with temperatures not falling below 30.8°F. Still, temperatures were below freezing for as much as 14 hours in parts of the Sherman County (Figure 2, upper panel). The morning of May 2nd was colder, but temperatures were not sustained below freezing for such a long period of time, and the longest time period with below-freezing temperatures was about 7.7 hours (Figure 2, lower panel).

Freeze damage to wheat is a function of minimum temperatures, duration of cold temperatures, and whether the cold temperature matches stages of crop development that are more sensitive to cold temperatures. Our estimates of growth stage in northwest Kansas indicate that the majority of the wheat is at or approaching flag leaf emergence, with some more advanced fields reaching the boot stage (Figure 3). During these stages, the temperature threshold below which freeze damage can be sustained is about 28°F.Temperatures below 28°F for longer than approximately 2 hours can cause floret sterility, trapped spikes, leaf damage, and possible damage to the lower stem.

Temperatures only reached levels below 28°F during the morning of May 2nd, for a maximum duration of about 1.7 consecutive hours. While these temperatures did not reach the 2-hour threshold suggested for freeze damage, these thresholds are somewhat flexible because actual freeze damage is function of many other factors, including the actual canopy temperature (function of density of the stand on each field and soil temperature) and micro-meteorology of each individual field (including residue cover, wind speed, soil moisture status, temperature gradients in the field, etc.).

Figure 2. Number of hours temperatures were below freezing (32°F) during April 29th- May 1st (upper panel) and May 1st – May 2nd (lower panel).
Figure 3. Estimated wheat growth stage as of April 29, 2016.
Figure 4. Number of hours temperatures were below 28°F during May 1st – May 2nd.

The above information indicates that some freeze damage may have been sustained in Sherman and Wallace counties and the surrounding region, most likely to fields further along in development. To assess freeze damage during the boot stage, producers should look for the following symptoms:

More information on freeze damage to wheat is available in Spring Freeze Injury to Kansas Wheat, K-State Research and Extension publication C646, available at:

Romulo Lollato, Wheat and Forages Specialist

Mary Knapp, Weather Data Library

Chip Redmond, Weather Data Library

Erick DeWolf, Extension Plant Pathology