wrote :
On 18 Jan, 20:36, Mike Tullett wrote:
On Fri, 18 Jan 2008 19:39:51 +0000, Trevor Harley wrote:

I really hate it when the temperature soars between 8 and 9 am. Quite
often in winter the maximum is 8.59 a.m. December 21st here was very
cold - a maximum of -2.4C during the day, dropping to -6.8C around 2
am, then climbing rapidly to -1.4C at 8.59, thus spoiling my record
lowest maximum. And there have been several occasions where an
otherwise "frost day" has been ruined by rising temperatures around
dawn (which is 8.45 a.m. here).

The most notable occasion that happened here was in the early 80s. The
daytime max was about -11C but by 0900 next day the temp was up to +3C.

I can remember in the cold spell at the end of January 1972, the
morning of 31 Jan was bitterly cold (my min that morning, in
Warwickshire, was -12.2°C, around 8.30 am). At around a third of
climatological sites in the Midlands, the lowest temperature occurred
a little after the (nominal) 0900 UTC observation, so the minimum
thermometer reading was, following standard practice, credited to the
following morning - i.e. 1 February. However, milder air spread in
quickly during the day on 31 January, and February was a mostly mild
month, resulting in most places seeing their official lowest February
(and annual) minimum occurring ... erm, in January.

snip
I remember that one too! At the time (and until approx 1983) the
MWR tabulated climatological stations with terminal hours of
09-09 alongside synoptic stations with terminal hours of 09-21-09,
leading to apparent huge differences between neighbouring sites -
eg in Nottinghamshire, Watnall -3.4°C and Warsop -13.8°C -
the first recorded overnight 31st/1st, and the second at 09z on
the 31st (presumably).

Philip