The Central England Temperature (CET) series is the longest available instrumental record of temperature in the world, with the monthly mean temperature extending back to 1659 and the daily mean temperature series extending back to 1772. The daily and monthly minimum and maximum temperature series extend back to 1878.

These historical temperature series have been constructed to provide a long running temperature record for the Central England region, a roughly triangular area of the United Kingdom enclosed by Somerset, Lancashire and London. The CET value is then calculated as an average of the recorded temperatures for a few stations which are selected as representative of the region as a whole. Although the selected stations have changed over time, due primarily to station closures, the series is homogenised to ensure that it remains consistent.

Stations used in the construction of the CET series between 1772 and 1852 include: Kennington, Crane Court, Lyndon Hall, Syon House, Somerset House, Greenwich Observatory, Chiswick.

Stations used in the construction of the CET series from 1853 onwards include: Radcliffe (Oxford), Cambridge (legacy), Ross-on-Wye, Rothamsted, Malvern, Stonyhurst, Ringway, Squires Gate, Pershore College.

Gordon Manley (1953, 1974) compiled most of the monthly series from 1659 to 1973, and the mean temperature series is adjusted up to 1973 to align with Manley's recorded daily mean temperature values. The series data were updated to 1991 by Parker et al (1992) and comprise the V2 series which is updated with the latest values. For latest updates please see Legg et al (2025).

After 1973, the series is adjusted to extend the alignment with Manley's series. Further adjustments are applied to homogenise the current station selection to that used by Manley as well as to account for urbanisation.

The version controlled CET series is updated annually (February-March), with the previous complete year’s values refreshed to ensure that data acquisition and quality control procedures have been completed and ensure the most accurate station temperature values are used. Each version of the dataset will include data up until the end of the previous complete year and an incremental version number will be updated.

The CET datasets employ the following version control protocol:

Version Vx.y.z.a:
• x – major changes – e.g. change in scientific methodology
• y – minor changes – e.g. small bug fixes or updates to diagnostics pages
• z – incremental changes
• a – reserved for use internally

The standard annual release cycle of CET will constitute an incremental release (z). However, if more substantial
changes have been made to the codebase, scientific methodology or source data values, then this may warrant a minor (y) or major (x) version release. (Note, these are applied to a cohort of datasets together - i.e. apply to the seasonal, monthly, daily and adjustment datasets as a coordinated version release).

This new version of the datasets will supersede the previous version.

A provisional version of the CET series, with recent data up to the previous day, is available for download on the Met Office Hadley Centre webpage: https://www.metoffice.gov.uk/hadobs/hadcet/data/download.html . Link also available in the list of online resources on this record.

Note: the v1.0.0.0 datasets within the collection on the CEDA archive were originally pulled over monthly from the Met Office Hadley Centre website on a monthly basis until the end of July 2022.