Finally we have a below average month and quite some way below as well. Coldest August since 1993. September looks like starting on a much warmer note and this warmer weather may stick around for most of the first half. But will it hold on for the second half of the month? Only time will tell.

Please post your September CET predictions in this thread. The deadline for entries without incurring any penalty is 23:59 on Sunday evening (31st). However, entries will be accepted up to 23:59 on 2 September.

September historic data summary

Here is the usual rundown of historic data for previous years.

September has for many years now often been a very warm month, or at least close to average. Only once since 1994 has the CET been more than 0.5C below the 1971-2000 mean and that was in 2012 with 13.0C. It has exceeded 15C on 4 occasions including the remarkable record of 16.8C set in 2006.

There has to be a good chance that 2014 will see the August CET cooler than both June and September. This has only ever happened three times in the history of the CET:

1737 Jun 15.9C Aug 13.8C Sep 14.2C
1865 Jun 15.6C Aug 15.1C Sep 16.3C
1891 Jun 14.7C Aug 14.1C Sep 14.2C

Interestingly this scenario has occurred once even where the Aug CET was at least 15C which was in 1865 as above. The other two years August was just incredibly cold. In 2014 the August CET will be close to 15C but there is a real chance it will still be cooler than both June and September. 

Long run averages:
1971-2000: 13.7C
1981-2010: 14.0C
1989-2013: 14.2C

Here is a chart of the September CET since 1961 with a 10 year moving average

Here are some details of what the models and forecasters generally are saying at the moment.

GEFS (850 and 2m temps)
http://www.wetterzentrale.de/pics/MT8_London_ens.png
http://www.wetterzentrale.de/pics/MT8_Manchester_ens.png
http://www.wetterzentrale.de/pics/MT2_Manchester_ens.png
http://www.wetterzentrale.de/pics/MT2_London_ens.png
Looking distinctly warm at the moment

ECM(De Bilt) maximum and minimum temps
http://www.knmi.nl/exp/pluim/vijftiendaagse/index.php
http://www.knmi.nl/exp/pluim/kansverwachtingen_staafdiagram.php?run=00&type=tn
http://www.knmi.nl/exp/pluim/kansverwachtingen_staafdiagram.php?run=00&type=tx
Also looks fairly warm. Today's 0z run was easily the coldest run by day 10

Met office
http://www.metoffice.gov.uk/public/weather/forecast
Generally warm in the south and nearer average in the north. Later in the warm it may become cooler at night. Daytime temperatures will be warm at times but also some cooler interludes.

Pattern matching (just for fun)
If we look at years with a summer CET between about 15.75C and 16.25C (2014 should come in around 16.0C) there are a lot of matches. So if I then take those years where the August CET was around 0.7C either side of 15C there are just 7 matches since 1900 including 2010.

Of these 9 all bar one had a September CET between 13.6C and 14.6C with only one above 14.2C. There was one cold year at 12.9C (1950). So this would suggest a fairly average CET for September this year. Remember though this is just for fun and not in any way scientific.  

Latest forecast September CET tracker

Can't do any worse than August. 14.93c thanks.

14.20c for me. Thanks

________________________________________________________________________________________________________

Gary

Have we had many incidences of the September being warmer than the August?

15.7 C for me, please.

Have we had many incidences of the September being warmer than the August?

14.5C for me please.

14.6c warm start to the month but with cold end with frosts.

Have we had many incidences of the September being warmer than the August?

Not many. 2006 is of course the best example in recent times. The only other time it has happened since 1900 is 1956. It happened two years in a row in 1890 and 1891. 1865 is another one

14.4C for me please

That's an interesting stat about the 1890s. They really were a colourful few years.

1890 coldest December on record

1892 coldest March

1890&91 September warmer than August.

1894-5 very severe winter

JFF fun of course, but do I detect a long term pattern match with the last 4 years...! Sounds familiar with recent years.

Dont tell the Daily Express though, they'll put the mockers on it

14.7C please.

I'll lgo for a warm start but much ccoler later - 14.0C overall

13.9 please

A mixed month: 14.1c please

14.75 please

14.8c please.

13.3 Thanks

(Remember guys, my guesses here are JFF)

My August guess was way too high but I'm not ready to give up on the summer weather yet

so I'm going for 15c  please