My coldest experience was 19th June 1973,in fact it was my first all nighter,the weather was hot.
I fished all night in shirtsleeves caught plenty of tench and bream but just as the sun came up, I started feeling cold and shivery,the only relief came when I went looking for the direct rays of the sun.
Never felt so bad,apart form food poisoning, but learnt a lesson.
The coldest hour is just before dawn.
Sounds like a good song title!!