11 June 2025
The Seasonal Normal Weather Review is an activity performed by Xoserve, as the Central Data Services Provider (CDSP), alongside the DESC, typically every five years.
The objective is to review, and where appropriate, revise the industry’s weather parameters which help us estimate gas consumption for the Non-Daily Metered sector throughout the year.
Reviewing the Composite Weather Variable (CWV) and the Seasonal Normal Composite Weather Variable (SNCWV)
The Seasonal Normal Weather Review involves reviewing the Composite Weather Variable (CWV), which represents actual weather, and the Seasonal Normal Composite Weather Variable (SNCWV), which represents a view of ‘normal’ weather. Both areas were reviewed extensively by Xoserve and the DESC during 2024.
- The CWV review has resulted in a set of freshly optimised definitions using up to date demand reactions and behaviours.
- The SNCWV review included a collaboration with the Met Office, whose meteorological expertise helped ensure the future values incorporated the impacts of climate change for the relevant period.
Reduction in Annual Quantities (AQs) due to warmer Seasonal Normal basis
The main headline from this process is that the majority of Local Distribution Zones (LDZs) are seeing a significant warming in the Seasonal Normal basis compared to current values – particularly during Spring.
This warming will result in a reduction in AQs, especially for those End User Categories (EUCs) which exhibit increased weather sensitivity, such as the domestic sector.
The outcomes of this year’s review will take effect from 1 October 2025 and remain in place until 30 September 2030.
Read our Seasonal Normal Weather Review 2025 document
For more information on our approach to the review, including our collaboration with the Met Office, read our accompanying document.
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Seasonal Normal Weather Review 2025The Seasonal Normal Weather Review is an activity performed by Xoserve, as the Central Data Services Provider (CDSP), alongside the DESC, typically every five years.
PDF, Last Updated 11/06/2025, 2.4 MB
Next steps and further information
You can find a high-level summary of the Seasonal Normal Weather Review so far on the dedicated Demand Estimation Sub-Committee webpage on the Joint Office website. This includes a link to the estimated impacts to AQs, presented to DESC earlier this year.
We’ll provide more updates in the coming months as we approach the implementation of the new values.
If you have any questions or comments on the Seasonal Normal Weather Review, please contact us at Xoserve.demand.estimation@xoserve.co.uk.
Our 2025 Seasonal Normal Weather Review
Read more about this year's approach and collaboration with the Met Office, in our 2025 Seasonal Normal Weather Review document.
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