We’re proper geeks when it comes to the winter temperatures. The met office has weather stations around the UK which keep records of temperatures. We use MET Office weather stations For cold weather observation to see how the cold affects the various species of bonsai tree which we keep. Over time, you can build up a picture of what happens through the cold season and how your bonsai trees have performed. Aids planning and preparation for future years of bonsai tree growing.
https://www.metoffice.gov.uk/public/weather/observation