Do I hear goalposts being shifted?
There is less tendency to deviate from the maximum in winter but very large scope for deviation from the minimum. Temperatures of around -15C are a bigger deviation from the average minimum (in England at least) than just about any record high temperature in the summer. And yet such temperatures were recorded quite widely in December. Assuming the average is around 1-2C, this represents a difference of 16-17C from the average. We've only seen that kind of deviation from the max in summer on two or three occasions (I'm thinking August 1990 and 2003). Of course even lower minima were experienced widely in Highland Scotland.