UK Weather Report–July 2012
By Paul Homewood
While the US has been basking in an unusually warm summer, the weather in the UK should remind us that there are two sides to every coin. If April through June had not been bad enough already, July has continued the cold and wet pattern. According to the Met Office, mean temperatures were 1.0C below the long term average at 14.1C. Since 1910, there have only been 29 colder months of July. As the above map indicates, maximum temperatures are even further down, with the Met Office showing a provisional figure of 17.8C, which is 1.6C colder than average.
As for rainfall, the month was not quite as wet as June, but still ended up 48% above normal. It is worth noting that the trend in recent years is back to the levels seen in the early part of the 20thC, before a drier interlude began in the 1960’s. It is highly unlikely, though, that the summer will set anything approaching a rainfall record, unless August is exceptionally wet.
Footnote
I have previously commented on the use of the 1971-2000 period for calculating averages, as the Met Office do. They have informed me that they are already in the middle of converting to 1981-2010 averages, which have been used on the above graphs and maps. Some of their data still uses the older period, but these should be changed over for next month.
Perhaps other organisations such as GISS should take note.
NOT A LOT OF PEOPLE KNOW THAT 
Personally I disagree with the use of any 30 year period average to define what is “normal”, since the figure is likely to vary significantly over different time periods.
I would prefer the use of the median value over the data series, which I feel provides a much more stable definition of “normality”.
For example, the 30 year year U.K. temperature July average has gone from 14.42c for 1961-90, to 14.86c for 1971-2000 and 15.16c for 1981-2010. Using this method, the definition of “normality” is constantly changing.
On the other hand, the median value has been between 14.4c and 14.5c since 1932 and has been 14.5c since 1990.
On that basis, this July was 0.4c below “normal”, whereas based on the 1981-2010 average, it was 1.06c below “normal”.
Using the same method for the July maximum temp., the median has been between 18.4c and 18.6c since 1944, and is currently 18.5c, compared to 30 year averages of 18.6c, 19.13c and 19.42c for the above 30 year periods.
On this basis, this July was 0.7c lower than “normal”, rather than 1.62c below “normal”, based on the 1981-2010 average.