Water and temperature affect many crop processes simultaneously ranging from crop growth, development, photosynthesis, respiration, water transpiration, grain fill, and nutrient cycling. The magnitude of high temperature or drought stress depends also on the stage of the crop. Another factor that should be considered is how high minimum temperatures are.
During July and August, warm nights may accelerate maturity of corn to the detriment of yield. In most areas of Iowa, 2015 and 2016 were much alike for corn. In this case, nighttime temperatures may indeed be the major factor resulting in a yield improvement or diminished yield in 2016 since warm nights accelerate maturity and thereby reduce yields.
Look at July and August—the period from silking to maturity. If nights are mainly warmer than usual (red) the yield is reduced. Nights cooler than usual (blue) tend to enhance yields.
