Cooling and heating degree days - Cities and FUAs — Cooling degree in Rennes
Rennes: Cooling and heating degree days - Cities and FUAs — Cooling degree was 41.35 Degree days in 2025. ◆ Volatile
Cooling and heating degree days - Cities and FUAs — Cooling degree in Rennes, 1950–2025
Source: Organisation for Economic Co-operation and Development. Measured in Degree days.
Analysis
Rennes recorded 41.35 Degree days for cooling and heating degree days - cities and fuas — cooling degree in 2025.
Compared with earlier readings it is up 6.5% on the previous year and down 18.8% over ten years.
Over the whole period, cooling and heating degree days - cities and fuas — cooling degree in Rennes peaked at 122.06 Degree days in 2022 and was at its lowest, 9.77 Degree days, in 1954.
That places Rennes 804th out of 1323 regions with data for 2025, putting it in the middle of the range.
The series is highly variable year to year, so single readings are best treated with caution.
Averages by decade
| Decade | Average | Lowest | Highest | Years |
|---|---|---|---|---|
| 1950s | 34.77 Degree days | 9.77 Degree days | 80.6 Degree days | 10 |
| 1960s | 28.57 Degree days | 10.68 Degree days | 54.4 Degree days | 10 |
| 1970s | 34.36 Degree days | 10.57 Degree days | 115.33 Degree days | 10 |
| 1980s | 36.44 Degree days | 13.53 Degree days | 72.78 Degree days | 10 |
| 1990s | 51.26 Degree days | 19.72 Degree days | 90.39 Degree days | 10 |
| 2000s | 48.72 Degree days | 12.41 Degree days | 115.42 Degree days | 10 |
| 2010s | 59.05 Degree days | 36.86 Degree days | 88.57 Degree days | 10 |
| 2020s | 68.04 Degree days | 38.81 Degree days | 122.06 Degree days | 6 |
More reference data data for Rennes
- Cooling and heating degree days - Cities and FUAs — Change in cooling -5.1 Degree days (2025)
- Cooling and heating degree days - Cities and FUAs 1,341 Degree days (2025)
- Cooling and heating degree days - Cities and FUAs — Change in heating -355.66 Degree days (2025)
- Precipitation - Cities and FUAs — Extreme precipitation days 2.6 Days per year (2024)
- Precipitation - Cities and FUAs — Change in extreme precipitation 0.0597 Days per year (2024)
- Dependency ratio - Cities and FUAs 21.7 Percentage of population aged 15-64 years (2022)
- Wind threats - Cities and FUAs — Exposure to wind threats 35.08 Percentage of area (2023)
- Coastal flooding - Cities and FUAs — Built-up area exposure to 0 Percentage of built-up area (2022)
- Main mode of transport to work - Cities and FUAs — Employed persons 115,472 Persons (2022)
- Internet speed - Cities and FUAs — Downloading speed 6.5 Percentage of national value (2025)
Frequently asked questions
- What is cooling and heating degree days - cities and fuas — cooling degree in Rennes?
- Cooling and heating degree days - cities and fuas — cooling degree in Rennes was 41.35 Degree days in 2025, according to Organisation for Economic Co-operation and Development.
- What is the highest cooling and heating degree days - cities and fuas — cooling degree recorded in Rennes?
- The highest recorded value was 122.06 Degree days in 2022.
- What is the lowest cooling and heating degree days - cities and fuas — cooling degree recorded in Rennes?
- The lowest recorded value was 9.77 Degree days in 1954.
- How does Rennes rank for cooling and heating degree days - cities and fuas — cooling degree?
- Rennes ranks 804th out of 1323 regions with data for 2025.
- Is cooling and heating degree days - cities and fuas — cooling degree rising or falling in Rennes?
- Over the last ten years it is down 18.8%. The long-run trend across the full record is volatile.
- Where does this Rennes data come from?
- The figures come from Organisation for Economic Co-operation and Development, published as part of Cooling and heating degree days - Cities and FUAs — Cooling degree days. Statizoid updates them automatically from the source API.
Download this data
CSV · JSON — 76 observations, free to reuse under OECD Terms and Conditions (attribution required).
About this data
<p align="justify">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.</p> <h3>Data sources and methodology</h3> <p align="justify"> The indicators use 0.1-degree resolution grids from the <a href=https://developers.google.com/earth-engine/datasets/catalog/ECMWF_ERA5_LAND_DAILY_AGGR>ERA5-Land dataset</a>. 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.</p> <p align="justify"> 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. </p> <h3>Defining FUAs and cities</h3> <p align="justify">The OECD, in cooperation with the EU, has developed a harmonised <a href="https://www.oecd.org/en/data/datasets/oecd-definition-of-cities-and-functional-urban-areas.html">definition of functional urban areas</a> (FUAs) to capture the economic and functional reach of cities based on daily commuting patterns <a href=https://doi.org/10.1787/9789264174108-en>(OECD, 2012)</a>. FUAs consist of: <ol> <li><b>A city</b> – defined by urban centres in the degree of urbanisation, adapted to the closest local administrative units to define a city.</li> <li><b>A commuting zone</b> – including all local areas where at least 15% of employed residents work in the city.</li> </ol> The delineation process includes: <ul> <li>Assigning municipalities surrounded by a single FUA to that FUA.</li> <li>Excluding non-contiguous municipalities.</li> </ul> <p> The correspondence table between SAUs and FUAs/cities is available in <a href=https://webfs-cfe.oecd.org/files/.Stat/cities_local_areas/fua_cities_sau_mapping.parquet>parquet </a> and <a href=https://webfs-cfe.oecd.org/files/.Stat/cities_local_areas/fua_cities_sau_mapping.csv>csv</a> format. </p> The definition identifies 1 272 FUAs and 1 269 cities in all OECD member countries except Costa Rica and three accession countries.</p> <h3>Cite this dataset</h3> <p>OECD Regions, cities and local areas database (<a href="http://data-explorer.oecd.org/s/1dj">Cooling and heating degree days - Cities and FUAs</a>), <a href=http://oe.cd/geostats>http://oe.cd/geostats</a></p> <h3>Further information</h3> <ul> <li> <a href=https://localdataportal.oecd.org/>OECD Local Data Portal </a> </li> <li> <a href=https://www.oecd.org/en/publications/oecd-regions-and-cities-at-a-glance-2024_f42db3bf-en.html/>OECD Regions and Cities at a Glance </a> </li> </ul> <p align="justify">For questions and/or comments, please email <a href="mailto:CitiesStat@oecd.org">CitiesStat@oecd.org</a>