I was wondering today whether there has ever been a winter (Dec, Jan &
Feb) where the temperature has not fallen below zero. Lets say somewhere
in the far south of England.

As you pointed out, if a winter is frost free, there is often a frost in
spring. To get around this, if we look at the calendar year, Southsea in 1974
failed to go lower than +0.2. Headlands on the west coast of Britain also
stayed above zero (Hartland Pt., Dale Fort, Bardsey Is.). One site on the west
coast of Scotland and one on an island (Islay) dropped only to 0.0. Some places
in Cornwall stayed above in the warm year of 1949 - and probably in other warm
years too.

Of course, winter 1973-74 might not have been frost free at Southsea, but the
Monthly Weather Reports of the Met Office show that there were air frosts in
Nov. and Dec. 1973 so the winter half-year 73-74 was not frost free.
Interesting case of a combination of a warm sea and urban warming effects. I
would not even dare to look up urban rooftop records ( :-) ) but London Weather
Centre must have come close in some years, as has St James's Park.

If warming continues as scenarios suggest, it will be intersting to see how
often the air frost free year occurs. It might occur in the the centres of
larger cities - if only they all still had (ground level) observing sites.
Maybe not this winter though, if journalists are to be believed....

Julian
Julian Mayes, Molesey, Surrey (still waiting for first air frost this season).