On Friday 07 Jan 2011 17:34, Ian Bingham scribbled:

My average temperature graph for January (1990-2010) shows low
temperatures at the beginning and end of the month and relatively high
temperatures at
mid-month. This appears to be due to the fact that every year in January
we seem to get a few days of more or less strong SWlies which of course
raises
the temperature appreciably. This has occurred at various times of the
month, so the average puts it in the middle, I suppose. For example I
have as 21-year means:
Jan 1st 2.1C
Jan 15th 4.4C
Jan 31st 2.3C


On a slightly larger scale, forty-odd years ago I extracted temperature data
for Arctic stations from the WMO 31-60 normals. Most stations only had the
51-60 period so that's a problem but many showed January to be warmer than
December or February. I think the bulk, if not all, of the stations showing
this feature were in the Soviet Arctic.

--
Graham Davis, Bracknell
It was raining cats and dogs and I fell in a poodle. [Chic
Murray(1919-1985)]