Cooling and heating degree days - Cities and FUAs — Cooling degree in Santa Barbara

About this data

Indicator

Cooling and heating degree days - Cities and FUAs — Cooling degree days

Unit

Degree days

Source

Organisation for Economic Co-operation and Development

Licence

OECD Terms and Conditions (attribution required)

Coverage

1,325 places, 100,700 data points, 1950–2025

Last refreshed

17 August 2026

This dataset provides indicators of Cooling and Heating Degree Days (CDDs and HDDs) for FUAs and cities. CDDs and HDDs are measurements used to estimate energy usage based on outdoor temperature. CDD measures the demand for cooling, while HDD measures the demand for heating, both calculated relative to a baseline temperature. Data sources and methodology The indicators use 0.1-degree resolution grids from the ERA5-Land dataset. ERA5-Land is used as it provides harmonised, globally consistent coverage at fine spatial resolution (0.1 degree), enabling the production of comparable subnational indicators also where national meteorological data are not available at the required scale. Annual CDDs are the sum over a year of the differences between the daily mean outdoor air temperature and the threshold temperature when the outdoor temperature is above the threshold temperature. HDDs are the sum over a year of the differences between the threshold temperature and the daily mean outdoor air temperature when the outdoor temperature is below the threshold temperature. Threshold temperatures are set to 22°C for CDDs and 15°C for HDDs. These estimates may differ from official subnational climate statistics due to differences in methodological approaches, such as the use of reanalysis based top down modelling versus in situ observations, along with variations in input data sources, spatial resolution, and the models and algorithms used to generate temperature estimates. Defining FUAs and cities The OECD, in cooperation with the EU, has developed a harmonised definition of functional urban areas (FUAs) to capture the economic and functional reach of cities based on daily commuting patterns (OECD, 2012). FUAs consist of: A city – defined by urban centres in the degree of urbanisation, adapted to the closest local administrative units to define a city. A commuting zone – including all local areas where at least 15% of employed residents work in the city. The delineation process includes: Assigning municipalities surrounded by a single FUA to that FUA. Excluding non-contiguous municipalities. The correspondence table between SAUs and FUAs/cities is available in parquet and csv format. The definition identifies 1 272 FUAs and 1 269 cities in all OECD member countries except Costa Rica and three accession countries. Cite this dataset OECD Regions, cities and local areas database (Cooling and heating degree days - Cities and FUAs), http://oe.cd/geostats Further information OECD Local Data Portal OECD Regions and Cities at a Glance For questions and/or comments, please email CitiesStat@oecd.org