A measure of how much the average of the daily high and low temperature is greater than a reference temperature (typically 18°C or 65°F). Cumulatively CDDs measure the intensity and duration of warmth and indicate how much ‘cooling’ is required by, say, UK energy companies suffering poor sales during warm weather. An average daily temperature of 23°C creates 5 CDDs towards the season’s aggregate. UK energy companies hedge against warm weather by purchasing call options indexed by CDDs. Each CDD has a notional value, the tick, and the payout occurs when the cumulative CDDs exceed the strike. See WINTER SEASON; HEATING DEGREE DAYS; COOLING SEASON; GROWING DEGREE DAYS.