New future-ready weather files for accurate, efficient building performance modelling.
What's new?
Easy online access
Our new Weather Data Selection Tool makes finding and purchasing the right files simpler than ever.
Updated baseline data
Uses historical weather observations from 1994–2023 for improved reliability. Please note that these new files are not required for compliance. You can still access the 2016 CIBSE Weather Data Sets which are required for Part L and Part O compliance - access now.
Future climate projections
Includes UK Climate Projections 2018 (UKCP18) projections for the 2030s, 2050s, and 2080s.
More climate zones
Expanded from 16 locations to 28 climate zones for more precise local modelling.
Improved solar data
Incorporates Copernicus Atmosphere Monitoring Service (CAMS) solar radiation data.
Please note that pricing has changed for this new release. View the updated pricing chart.
For more information on the 2025 CIBSE Weather Data release please see CIBSE's Technical Briefing Document.
Find and purchase your weather data
Our selection tool helps you quickly identify the right zone and file for your project:
- Step 1: Enter your project’s location
- Step 2: Select your climate zone
- Step 3: Answer a few quick questions about your modelling requirements
"What is Weather Data?" and other FAQs
The UK Meteorological Office collects weather data at stations across the UK. Climate variables measured at hourly intervals include air temperatures, wind speed and direction and air pressure etc.
The weather variables are statistically analysed and morphed for 28 climatic zones across the UK. These are then provided in two data types:
- Design Summer Year (DSY)
- Test Reference Year (TRY)
DSYs and TRYs are used as climate inputs into building simulation software.
TRYs represent a typical weather year and should be used to conduct annual energy assessments.
DSYs are years with various hot weather events and should be used assess overheating risk.
For a more detailed explanation of the different types of weather files available and to better understand how the 2025 release compares to the 2016 release please see CIBSE's Technical Briefing Document.
Have any further questions? Email [email protected]
TRY
TRYs represent a typical weather year and should be used to conduct annual energy assessments.
DSY
DSYs are years with various hot weather events and should be used to conduct overheating risk assessments. There are three types of DSY files available (DSY1, 2 and 3) representing different hot weather events:
DSY1: a moderate year containing heat events with a return period of 7 years.
DSY2: the year containing the most intense heat events.
DSY3: the year containing the longest heat events.
Hourly data over a year are included in each file for the following weather variables:
- Dry Bulb Temperature (°C)
- Dew Point Temperature (°C)
- Relative Humidity (%)
- Atmospheric Station Pressure (Pa)
- Extraterrestrial Horizontal radiation (W/m2)
- Extraterrestrial Direct Normal Radiation (W/m2)
- Infrared Radiation intensity (W/m2)
- Global horizontal radiation (W/m2)
- Direct normal radiation (W/m2)
- Diffuse horizontal radiation (W/m2)
- Global Horizontal Illuminance (lx)
- Direct Normal Illuminance (lx)
- Diffuse Horizontal Illuminance (lx)
- Zenith Luminance (Cd/m2)
- Wind Direction (°)
- Wind Speed (m/s)
- Cloud Cover (10ths)
Timelines, Emissions and Percentiles
TRYs and DSYs are available for differing time periods, emission scenarios and probability percentiles (10th, 50th & 90th) to account for the variability and uncertainty in climate projections.
CIBSEs TRYs and DSYs (1-3) are provided for:
- three time periods: 2030s (2019–2039), 2050s (2039-2059), and 2080s (2069–2089),
- for the following emissions scenarios and probability percentiles:
- 2030s: High (RCP 8.5) – 50th probability percentile
- 2050s: High (RCP 8.5) and Med (RCP 4.5) – 10th, 50th & 90th probability percentiles
- 2080s: High (RCP 8.5), Med (RCP 4.5) and Low (RCP 2.6) - 10th, 50th & 90th probability percentiles
For more information download the Technical Briefing Document
View all CIBSE weather data packages [PDF]
Members of CIBSE receive 10% off. This discount will be applied after ordering - simply include your membership number in your order form.
Use the selection tool to browse the different package options or email [email protected]
- Select the data sets using the new selection tool.
- Fill out the order form.
- After ordering, you will be sent a link to pay within two days.
- Once you have completed the payment you will be able to find your new data sets in the My Downloads area of the MyCIBSE portal.
Note: Prepayment for Weather Data sets is required before sets are made available to purchasers.
For advice on which packages to choose please email our team at [email protected].
Weather Data Webinars
New weather data launch webinar
27 August 2025 12:00 - 13:00 (BST) Discover what’s new in the CIBSE Weather Data during our launch webinar, covering key updates, climate zones, and complian...
Learn more
Weather Data and compliance
The new CIBSE weather files are not mandatory for regulatory compliance. However, CIBSE will recommend using the 2025 release of weather data for building performance analysis during the design stage. We anticipate that after industry review and testing they will become widely adopted.
You can still access the 2016 CIBSE Weather Data Sets which are required for Part L and Part O compliance - access now.
- The “current” weather files are replaced by the new 2030s time period (covering 2019–2039).
- Future climate files are provided for the 2050s and 2080s.
- The dataset improves assessments for overheating, energy use, and climate resilience.
CIBSEs TRYs and DSYs (1-3) are provided for:
- three time periods: 2030s (2019–2039), 2050s (2039-2059), and 2080s (2069–2089),
- for the following emissions scenarios and probability percentiles:
- 2030s: High (RCP 8.5) – 50th probability percentile
- 2050s: High (RCP 8.5) and Med (RCP 4.5) – 10th, 50th & 90th probability percentiles
- 2080s: High (RCP 8.5), Med (RCP 4.5) and Low (RCP 2.6) - 10th, 50th & 90th probability percentiles
UK Meteorological Office
Further information on the Met Office’s range of services for construction can be found on their website.
Find out more