In addition to the Central England Temperature (CET) the Hadley Centre is monitoring the average monthly rainfall over England and Wales. The rainfall history goes back until 1766 and is one of the longest rainfall records in the world. As with
temperature actual monthly rainfall will be compared against a 30-year average known as the standard reference period. However, with every new decade this period will be shifted ten years further ahead. For example, in the year 2001 the old 1961-1990 reference has been replaced by the 1971-2000 period.
Comparing them provides a lot of important facts on how our most recent climate might have changed. For example, if you compare the 1961-1990 average rainfall with the period of 1971-2000, you will find that England and Wales turned slightly wetter over the last 30 years. Mean total annual r
ainfall increased from 915mm to 926.9mm. This is about 1.3% and doesn't seem much at all. However, autumn (September, October, November) and winter (December, January and February) turned significantly wetter, while spring (March, April and May) and summer (July, August and September) became slightly drier. Autumnal rainfall increased from 257.9mm to 270.3mm - which is about 5.2%, and winter rainfall by about 4.3%.
Also extreme months turned even a little more extreme. Between 1961 and 1990 the driest month was April 1984 with a total of 10.8mm and wettest October 1987 with a total of 180.2mm. Both months have been outranked by October 2000, totalling 188mm and dry August 1995 with a mere 9.1mm.
