Cooling Degree Days

Cooling degree day (CDD) is an index used to relate the day's temperature to the energy demands of air conditioning. CDDs are calculated by subtracting 65 from a day's average temperature. For example, on a day with an average temperature of 80°F, the CDD value is 15 (80 – 65 base = 15 CDD). If the temperature is lower than 65°F, the value of the CDD is zero. As with HDD, CDD can be added over periods of time to provide an estimate of seasonal cooling requirements.

The CDD forecasts are issued for major U.S. cities, which are traded on the Chicago Mercantile Exchange (CME). For non-U.S. cities, the summer months CDD is referred to as CAT. Our CDD forecasts are first available for paid subscribers only. All other subscribers can have access to those forecasts after the start of the calendar season, i.e., June 1st.

Since our temperature forecasts are currently prepared primarily for the calendar summer season (June-August), the CDD forecasts are issued for the same season. Occasionally, however, we also issue CDD forecasts for individual months within the cooling season, May through September. These "forecasts by opportunity" are available for paid subscribers only.

The skill scores presented here are for mean seasonal CDD forecasts. The observed values are settlement data reported by the CME. Click here to see how skill scores are calculated.