Early Morning Temperatures Apr 22 May Impact Some Wheat Growing Areas in KY

Carrie Knott, Extension Grain Crop Agronomist

Figure 1. Minimum air temperatures at 2 meters for the early morning hours of April 22, 2024 across Kentucky. Data obtained from KY Mesonet http://www.kymesonet.org/.

Across Kentucky, virtually all the wheat crop is late boot, heading or in many areas beginning to flower. The early morning low temperatures Apr 22 were quite literally frosty. In some areas, the low temperatures (Figure 1; Table 1; Table 2) were in the range that could potentially cause damage to the wheat crop (Table 3). Although the minimum air temperature recorded at 2.0 meters may not have fallen to or below the critical temperatures that may cause wheat damage, it is likely that the temperature was lower at the height of the wheat heads as illustrated for many of the KY Mesonet Temperature Inversion sites (Table 2). Therefore, it will be important to scout for freeze damage prior to making decisions on the profitability of applying wheat head fungicides this year.

It will take at least five to seven days with high temperatures of at least 40°F to be able to see damage. Given this week’s forecast, we should be able to easily see freeze damage as early as Monday April 29.

Table 1. Minimum air temperature at 2 meters and the approximate number of hours temperatures were less than or equal to 32°F and 30°F for all available KY Mesonet sites overnight March 21 to the early morning hours of April 22, 2024. Data obtained from KY Mesonet http://www.kymesonet.org/.

Table 2. Minimum air temperature and the approximate number of hours temperatures were less than or equal to 32°F and 30°F at 0.5 and 2.0 meter at all KY Mesonet temperature inversion sites overnight March 21 to the early morning hours of April 22, 2024. Data obtained from KY Mesonet http://www.kymesonet.org/.