http://www.onwar.com/chrono/1940/jan40/f28jan40.htm
Soviet moves distract Finn offensive
Sunday, January 28, 1940 www.onwar.com
The Winter War... The Finnish 9th Division attacks the Soviet 54th Division near Kuhmo and succeeds in splitting the Soviet force into three separate groups. The Finns are not able to press their attacks home. They are further distracted by relief attempts by the Soviet 23rd Division.
In Britain... The Director of Censorship permits newspapers to belatedly reveal details of Britain’s coldest winter since 1894. The Thames River ad the Southampton Docks were frozen and temperatures of -18° C (-33° F) were recorded at Buxton (Derbys).
If I remember my math and conversion formula, -18 C means 18 centigrade degrees below freezing, which in Fahrenheit is 32 degrees below freezing = zero Fahrenheit.
Over a few days, that's plenty cold enough to freeze the Thames.
It would be interesting to learn how often since then London temperatures have reached zero F, and when was the last time?