https://en.wikipedia.org/wiki/User:W...Bonington_1989
Although this was a sunny year, the weather station is located near a coal power station so in some years there is very low sun hours. In December 1989 there was only 13.8 hours of sunshine
I give it an E, its usual rating for 1981-2010. However in 1981-2010 it is only just an E, being so dull and June only just having enough sun hours to stop it being an F.