A modification of growing degree-days (GDD) with both upper and lower temperature thresholds. All temperatures above 86°F (30°C) are set to 86°F (30°C) and all temperatures below 50°F (10°C) are set to 50°F (10°C) before calculation of daily mean temperature. The reference temperature (base temperature) for corn heat units is 50°F (10°C). See degree-day.