Tomorrow’s weather forecast on its own is of limited use, we also need to know if the forecast weather is surprising or unusual - has it happened before? To make best use of weather forecasts and climate projections we need records of past weather to put them in context, and if we need good statistics for unusual events (storms, heatwaves, …) we need long records to provide enough observations.

One good source of such past weather data is the long reanalyses (for example 20CR and CERA-20C) which use weather-forecast models, constrained by observations of surface pressure, to produce estimates of past weather back to at least 1900. In times and places where climate databases contain many weather observations, these reanalyses produce precise estimates of past weather, but where there are few observations the reanalyses are very uncertain.

Reanalyses of the weather around the British Isles should be very good, as the region has as many historical observations as anywhere in the world; with government, marine, and amateur observations being made in quantity back to at least about 1850. Unfortunately, however, very few of the observations made 100 or so years ago are available to science: Records from them remain, but only on paper, in library and archive collections; they have never been digitised.

This dataset is an attempt to remedy this - it assembles 3.7 million recently-digitised historical observations, from the region around the UK, over the period 1851-1960, and presents them in a consistent format for easy scientific use.