There were around 3,688 heating degree-days in the United States in 2024. Degree-days are relative measurements of outdoor air temperature. Heating degree-days are deviations below the mean daily temperature of 65 degrees Fahrenheit (ca. 18 degree Celsius). Heating degree-days were more numerous in the mid 20th century.

This dataset contains global gridded maps of Heating Degree Days (HDD) and Cooling Degree Days (CDD) for three climate scenarios: a historical scenario corresponding to a global mean temperature rise of 1.0°C above pre-industrial levels (based on observations from 2006 to 2016), and two future climate projections for global mean temperature increases of 1.5°C and 2.0°C, respectively, regardless of when these thresholds are reached. HDD and CDD are widely used indicators to measure how much the mean temperature exceeds a reference temperature each day over a given period. They are widely used indicators to examine global temperature-related climate and quantify heating and cooling demand.

Five different maps of HDD and CDD are available for each scenario as NetCDF V4 files (*.nc). These maps relate to different annual statistical indices calculated using 70 climate simulations over a 10-year period: mean, median, 10th percentile, 90th percentile, and standard deviation. The novelty of this dataset lies in the combination of two factors: the representation of global mean temperature rise scenarios for 1.5°C and 2.0°C globally, regardless of when these occur; and the bias-corrected global climate dataset used to calculate HDD and CDD, which involves a large ensemble size at a high global spatio-temporal resolution.

Methods:

The global gridded statistical maps of HDD and CDD were calculated considering 18°C as the baseline temperature. First, the annual HDD and CDD were calculated for each simulated year of each scenario at all geographic locations (a total of 700 simulated years per scenario). Then, the statistical indices across this variability were obtained. Global gridded maps have a spatial resolution of 0.833° x 0.556° (longitude x latitude) over the land surface.

Climate data used:

These global gridded maps of CDD and HDD were calculated using bias-corrected global climate simulations for mean temperature generated using the HadAM4 Atmosphere-only General Circulation Model (AGCM) from the UK Met Office Hadley Centre. Each scenario involved an ensemble of 70 individual members with 6-hourly mean temperatures at a horizontal resolution of 0.833 longitude and 0.556 latitude for a 10-year period (700 runs per scenario), aiming to ensure internal climate variability. These simulation experiments were run within the climateprediction.net (CPDN) climate simulation environment, using the Berkeley Open Infrastructure for Network Computing (BOINC) framework to distribute a large number of individual computational tasks. This system utilises the computational power of publicly volunteered computers that are globally distributed. The bias-corrected global climate dataset used to calculate these CDD and HDD maps is available at:

Lizana, J.; Miranda, N.D.; Sparrow, S.; Zachau-Walker, M.; Watson, P.; Wallom, D.C.H.; McCulloch, M. (2023): Large ensemble of global mean temperatures: 6-hourly HadAM4 model run data using the Climateprediction.net platform. NERC EDS Centre for Environmental Data Analysis, 28 June 2023. doi:10.5285/9c41e3aa67024bbdad796290a861e968

Heating degree day (HDD) index is a weather-based technical index designed to describe the need for the heating energy requirements of buildings. Cooling degree day (CDD) index is a weather-based technical index designed to describe the need for the cooling (air-conditioning) requirements of buildings.

HDD and CDD are derived from meteorological observations of air temperature, interpolated to regular grids at 25 km resolution for Europe. Calculated gridded HDD and CDD are aggregated and subsequently presented on NUTS-3 level.

This dataset includes monthly data as published by the Joint Research Centre's AGRI4CAST Resources Portal (Note that Eurostat is not the producer of the monthly data, but is only re-publishing them). Annual data are calculated as sum of monthly data by Eurostat.

Contained within the 5th Edition (1978 to 1995) of the National Atlas of Canada is a map that shows the annual sum of heating degree days (an indicator of building heating needs). Data for period 1941 to 1970. Companion sheet to Frost-Free Period, Growing Degree-Days, Last Frost in Spring and First Frost in Autumn.

Jordan Heating Degree Days data was reported at 1,798.380 Degrees Celsius in 2020. This records a decrease from the previous number of 1,954.970 Degrees Celsius for 2019. Jordan Heating Degree Days data is updated yearly, averaging 2,098.020 Degrees Celsius from Dec 1970 (Median) to 2020, with 51 observations. The data reached an all-time high of 2,798.670 Degrees Celsius in 1992 and a record low of 1,310.030 Degrees Celsius in 2010. Jordan Heating Degree Days data remains active status in CEIC and is reported by World Bank. The data is categorized under Global Database’s Jordan – Table JO.World Bank.WDI: Environmental: Climate Risk. A heating degree day (HDD) is a measurement designed to track energy use. It is the number of degrees that a day's average temperature is below 18°C (65°F). Daily degree days are accumulated to obtain annual values.;World Bank, Climate Change Knowledge Portal. https://climateknowledgeportal.worldbank.org;;

Malaysia Heating Degree Days data was reported at 0.000 Degrees Celsius in 2020. This stayed constant from the previous number of 0.000 Degrees Celsius for 2019. Malaysia Heating Degree Days data is updated yearly, averaging 0.020 Degrees Celsius from Dec 1970 (Median) to 2020, with 51 observations. The data reached an all-time high of 0.290 Degrees Celsius in 1971 and a record low of 0.000 Degrees Celsius in 2020. Malaysia Heating Degree Days data remains active status in CEIC and is reported by World Bank. The data is categorized under Global Database’s Malaysia – Table MY.World Bank.WDI: Environmental: Climate Risk. A heating degree day (HDD) is a measurement designed to track energy use. It is the number of degrees that a day's average temperature is below 18°C (65°F). Daily degree days are accumulated to obtain annual values.;World Bank, Climate Change Knowledge Portal. https://climateknowledgeportal.worldbank.org;;

The greatest number of heating degree days (HDDs) in the United Kingdom is usually recorded in January and February of each year. In 2023, there were 10.2 HDDs in January, which was a slight decrease from the previous year. The highest number of HDDs during the period in consideration was recorded in February 2018, at 12.4 days. The following year, this figure dropped to some 8.6 HDDs.

Heating homes

Heating degree days are defined as days in which the average temperature is less than 15.5 degrees Celsius. They are used to help measure the demand for energy required to heat buildings. In the United Kingdom, the most common way to heat properties is by far gas central heating.

Cold winters

In January 2023, the average temperature in the UK dropped to just 2.9 degrees Celsius. This was the lowest average monthly temperature recorded since January 2021. That same month, there were 10.7 air frost days across the country, slightly up from 10.2 air frost days recorded in the same month of the previous year. Air frost days are when the minimum air temperature falls below zero degrees Celsius.

The average number of heating degree days in the United Kingdom (UK) peaked in 2010 at 6.8 days, followed by 6.2 days in 2013. In 2021, the average number of heating degree days amounted to 5.5.

Nigeria Heating Degree Days data was reported at 3.170 Degrees Celsius in 2020. This records an increase from the previous number of 0.240 Degrees Celsius for 2019. Nigeria Heating Degree Days data is updated yearly, averaging 1.270 Degrees Celsius from Dec 1970 (Median) to 2020, with 51 observations. The data reached an all-time high of 9.880 Degrees Celsius in 1983 and a record low of 0.120 Degrees Celsius in 2009. Nigeria Heating Degree Days data remains active status in CEIC and is reported by World Bank. The data is categorized under Global Database’s Nigeria – Table NG.World Bank.WDI: Environmental: Climate Risk. A heating degree day (HDD) is a measurement designed to track energy use. It is the number of degrees that a day's average temperature is below 18°C (65°F). Daily degree days are accumulated to obtain annual values.;World Bank, Climate Change Knowledge Portal. https://climateknowledgeportal.worldbank.org;;

[Updated 28/01/25 to fix an issue in the ‘Lower’ values, which were not fully representing the range of uncertainty. ‘Median’ and ‘Higher’ values remain unchanged. The size of the change varies by grid cell and fixed period/global warming levels but the average percentage change between the 'lower' values before and after this update is -1%.]What does the data show? A Heating Degree Day (HDD) is a day in which the average temperature is below 15.5°C. It is the number of degrees above this threshold that counts as a Heating Degree Day. For example if the average temperature for a specific day is 15°C, this would contribute 0.5 Heating Degree Days to the annual sum, alternatively an average temperature of 10.5°C would contribute 5 Heating Degree Days. Given the data shows the annual sum of Heating Degree Days, this value can be above 365 in some parts of the UK.Annual Heating Degree Days is calculated for two baseline (historical) periods 1981-2000 (corresponding to 0.51°C warming) and 2001-2020 (corresponding to 0.87°C warming) and for global warming levels of 1.5°C, 2.0°C, 2.5°C, 3.0°C, 4.0°C above the pre-industrial (1850-1900) period. This enables users to compare the future number of HDD to previous values.What are the possible societal impacts?Heating Degree Days indicate the energy demand for heating due to cold days. A higher number of HDD means an increase in power consumption for heating, therefore this index is useful for predicting future changes in energy demand for heating.What is a global warming level?Annual Heating Degree Days are calculated from the UKCP18 regional climate projections using the high emissions scenario (RCP 8.5) where greenhouse gas emissions continue to grow. Instead of considering future climate change during specific time periods (e.g. decades) for this scenario, the dataset is calculated at various levels of global warming relative to the pre-industrial (1850-1900) period. The world has already warmed by around 1.1°C (between 1850–1900 and 2011–2020), whilst this dataset allows for the exploration of greater levels of warming. The global warming levels available in this dataset are 1.5°C, 2°C, 2.5°C, 3°C and 4°C. The data at each warming level was calculated using a 21 year period. These 21 year periods are calculated by taking 10 years either side of the first year at which the global warming level is reached. This time will be different for different model ensemble members. To calculate the value for the Annual Heating Degree Days, an average is taken across the 21 year period. Therefore, the Annual Heating Degree Days show the number of heating degree days that could occur each year, for each given level of warming. We cannot provide a precise likelihood for particular emission scenarios being followed in the real world future. However, we do note that RCP8.5 corresponds to emissions considerably above those expected with current international policy agreements. The results are also expressed for several global warming levels because we do not yet know which level will be reached in the real climate as it will depend on future greenhouse emission choices and the sensitivity of the climate system, which is uncertain. Estimates based on the assumption of current international agreements on greenhouse gas emissions suggest a median warming level in the region of 2.4-2.8°C, but it could either be higher or lower than this level.What are the naming conventions and how do I explore the data?This data contains a field for each warming level and two baselines. They are named ‘HDD’ (Heating Degree Days), the warming level or baseline, and 'upper' 'median' or 'lower' as per the description below. E.g. 'HDD 2.5 median' is the median value for the 2.5°C projection. Decimal points are included in field aliases but not field names e.g. 'HDD 2.5 median' is 'HDD_25_median'. To understand how to explore the data, see this page: https://storymaps.arcgis.com/stories/457e7a2bc73e40b089fac0e47c63a578Please note, if viewing in ArcGIS Map Viewer, the map will default to ‘HDD 2.0°C median’ values.What do the ‘median’, ‘upper’, and ‘lower’ values mean?Climate models are numerical representations of the climate system. To capture uncertainty in projections for the future, an ensemble, or group, of climate models are run. Each ensemble member has slightly different starting conditions or model set-ups. Considering all of the model outcomes gives users a range of plausible conditions which could occur in the future. For this dataset, the model projections consist of 12 separate ensemble members. To select which ensemble members to use, Annual Heating Degree Days were calculated for each ensemble member and they were then ranked in order from lowest to highest for each location. The ‘lower’ fields are the second lowest ranked ensemble member. The ‘upper’ fields are the second highest ranked ensemble member. The ‘median’ field is the central value of the ensemble.This gives a median value, and a spread of the ensemble members indicating the range of possible outcomes in the projections. This spread of outputs can be used to infer the uncertainty in the projections. The larger the difference between the lower and upper fields, the greater the uncertainty.‘Lower’, ‘median’ and ‘upper’ are also given for the baseline periods as these values also come from the model that was used to produce the projections. This allows a fair comparison between the model projections and recent past. Useful linksThis dataset was calculated following the methodology in the ‘Future Changes to high impact weather in the UK’ report and uses the same temperature thresholds as the 'State of the UK Climate' report.Further information on the UK Climate Projections (UKCP).Further information on understanding climate data within the Met Office Climate Data Portal.

Romania Heating Degree Days data was reported at 5,357.060 Degrees Celsius in 2020. This records an increase from the previous number of 5,202.560 Degrees Celsius for 2019. Romania Heating Degree Days data is updated yearly, averaging 6,233.850 Degrees Celsius from Dec 1970 (Median) to 2020, with 51 observations. The data reached an all-time high of 7,055.300 Degrees Celsius in 1985 and a record low of 5,202.560 Degrees Celsius in 2019. Romania Heating Degree Days data remains active status in CEIC and is reported by World Bank. The data is categorized under Global Database’s Romania – Table RO.World Bank.WDI: Environmental: Climate Risk. A heating degree day (HDD) is a measurement designed to track energy use. It is the number of degrees that a day's average temperature is below 18°C (65°F). Daily degree days are accumulated to obtain annual values.;World Bank, Climate Change Knowledge Portal. https://climateknowledgeportal.worldbank.org;;

Users are recommended to consult the author (malcolm.mistry@unive.it / malmistry1977@gmail.com) for an updated version which includes more recent years. Monthly and Annual Cooling/Heating degree-days (CDD/HDD) using daily average temperature (°C), and Cooling degree-days using daily average wet-bulb temperature (Twb), based on the following threshold (base) temperatures: […]

This indicator shows how heating and cooling degree days have changed by state, based on a comparison of the first 65 years of available data (1895–1959) with the most recent 64 years (1960–2023). For more information: https://www.epa.gov/climate-indicators.

North Macedonia Heating Degree Days data was reported at 4,918.830 Degrees Celsius in 2020. This records an increase from the previous number of 4,735.090 Degrees Celsius for 2019. North Macedonia Heating Degree Days data is updated yearly, averaging 5,572.760 Degrees Celsius from Dec 1970 (Median) to 2020, with 51 observations. The data reached an all-time high of 6,146.050 Degrees Celsius in 1991 and a record low of 4,635.780 Degrees Celsius in 2018. North Macedonia Heating Degree Days data remains active status in CEIC and is reported by World Bank. The data is categorized under Global Database’s North Macedonia – Table MK.World Bank.WDI: Environmental: Climate Risk. A heating degree day (HDD) is a measurement designed to track energy use. It is the number of degrees that a day's average temperature is below 18°C (65°F). Daily degree days are accumulated to obtain annual values.;World Bank, Climate Change Knowledge Portal. https://climateknowledgeportal.worldbank.org;;

Ghana Heating Degree Days data was reported at 0.000 Degrees Celsius in 2020. This stayed constant from the previous number of 0.000 Degrees Celsius for 2019. Ghana Heating Degree Days data is updated yearly, averaging 0.000 Degrees Celsius from Dec 1970 (Median) to 2020, with 51 observations. The data reached an all-time high of 0.000 Degrees Celsius in 2020 and a record low of 0.000 Degrees Celsius in 2020. Ghana Heating Degree Days data remains active status in CEIC and is reported by World Bank. The data is categorized under Global Database’s Ghana – Table GH.World Bank.WDI: Environmental: Climate Risk. A heating degree day (HDD) is a measurement designed to track energy use. It is the number of degrees that a day's average temperature is below 18°C (65°F). Daily degree days are accumulated to obtain annual values.;World Bank, Climate Change Knowledge Portal. https://climateknowledgeportal.worldbank.org;;

This dataset consists of four different variables: degree days below 65°F (or "heating degree days"), degree days below 0°F, degree days below 32°F (or "air freezing index"), and degree days above 32°F (or "air thawing index"). All were derived from the same set of nine statistically downscaled CMIP5 global climate model outputs driven by RCP 4.5 and RCP 8.5 emissions scenarios. A historical baseline (Daymet, 1980-2017) dataset is included for each variable. All data are in GeoTIFF format and have a spatial resolution of 12 km.

Units are degree days Fahrenheit (°F⋅days).

The model-scenario combinations are: - ACCESS1-3, RCP 4.5 - ACCESS1-3, RCP 8.5 - CanESM2, RCP 4.5 - CanESM2, RCP 8.5 - CCSM4, RCP 4.5 - CCSM4, RCP 8.5 - CSIRO-Mk3-6-0, RCP 4.5 - CSIRO-Mk3-6-0, RCP 8.5 - GFDL-ESM2M, RCP 4.5 - GFDL-ESM2M, RCP 8.5 - inmcm4, RCP 4.5 - inmcm4, RCP 8.5 - MIROC5, RCP 4.5 - MIROC5, RCP 8.5 - MPI-ESM-MR, RCP 4.5 - MPI-ESM-MR, RCP 8.5 - MRI-CGCM3, RCP 4.5 - MRI-CGCM3, RCP 8.5

The .zip files that are available for download are organized by variable. One .zip file has all the models and scenarios and years for that variable. Each GeoTIFF file has a naming convention like this:

"ncar_12km_{model}_{scenario}_{variable}_{year}_Fdays.tif"

Each GeoTIFF has a 12 km by 12 km pixel size, and is projected to EPSG:3338 (Alaska Albers).

New Zealand Heating Degree Days data was reported at 4,926.870 Degrees Celsius in 2020. This records an increase from the previous number of 4,868.990 Degrees Celsius for 2019. New Zealand Heating Degree Days data is updated yearly, averaging 5,247.730 Degrees Celsius from Dec 1970 (Median) to 2020, with 51 observations. The data reached an all-time high of 6,054.520 Degrees Celsius in 1992 and a record low of 4,868.990 Degrees Celsius in 2019. New Zealand Heating Degree Days data remains active status in CEIC and is reported by World Bank. The data is categorized under Global Database’s New Zealand – Table NZ.World Bank.WDI: Environmental: Climate Risk. A heating degree day (HDD) is a measurement designed to track energy use. It is the number of degrees that a day's average temperature is below 18°C (65°F). Daily degree days are accumulated to obtain annual values.;World Bank, Climate Change Knowledge Portal. https://climateknowledgeportal.worldbank.org;;

This API provides data back to 1990 and projections annually, monthly, and quarterly for 18 months. It provides data on U.S. heating degree days and cooling degree days. Users of the EIA API are required to obtain an API Key via this registration form: http://www.eia.gov/beta/api/register.cfm

Paneuropean maps of climate change indicators (e.g. heating degree days) for different climate scenarios (historical, SSP1-2.6, SSP2-4.5, SSP5-8.5) and time horizons (reference, short time-horizon, medium time-horizon, long time-horizon) derived from CMIP6 climate data.