Roger has collected a large set of weather observations covering the past 150 years from various sources in East Berkshire, including Met Office weather stations and a set of amateur observations. I was quite surprised to see the strength of the trend in the resulting time series, with a strong warming over the past 30 years or so, and lots of variability. Lots of visitors to the festival felt it helped them understand how the climate may be changing for them and their region and put recent weather into a longer term context.
Update (07/06/12): You can also now see the month by month temperature timeseries.
Update (07/06/12): Two versions of the data are now shown below – the first is from the weather festival and very wide – the second is perhaps more suitable for viewing.