20 years ago this morning, some people would have woke up opened the front door and wonder if the UK had suddenly moved to the tropics because it was an outrageously mild night that night. 

On the 10th of December 1994, a pool of very mild tropical maritime air flooded the UK behind a warm front on southwesterly winds from a source near the Azores. Despite the general cloud cover, daytime maxima soared to exceptional levels for the time of the year on the 11th. Penkridge in Staffordshire recorded 17.7C on the 11th, a record maxima for that date. Other notable maxima during that period included,
Worcester, Sheffield: 17.6C
Prestatyn: 16.7C
Tynemouth: 16.4C
Heathrow: 15.4C
Birmingham: 15.2C
Manchester: 15.1C
There were large rainfall totals in the NW due to orthographic lifting. 170mm fell near Loch Lomond, 71.8mm at Glasgow, 54.4mm at Eskdalemuir, all on the 10th. Unsurprisingly, there was extensive flooding in these areas.
A cold front slowly pushing southwards on the 12th, cut off the very mild southwesterly flow and temperatures returned to near normal values. Such is the fickleness of the British weather, that whilst Hereford and Worcestershire recorded maxima between 15-17C on the 11th, some parts of the county had sub-zero maxima on the 23rd.

11th December 1994: 15C as a minimum at Tynemouth! Record December high minima as mentioned by Michael Fish in his Countryfile broadcast.
http://www.youtube.com/watch?v=Vaq1pQ2t-5Y

I remember that weekend well. As Kevin's post implies, it never stopped raining here for the best part of two days and there was some pretty bad flooding not far from where I live.

Despite that weekend being so mild and so wet and the 1994-95 winter generally being mild, it did serve up more interest for the cold loving fraternity that the sorry excuse for a winter that was 2013-14 ever did.