I have been on some of the highest places in great Britain in some of the most atrocious weather that mother nature can through at you, so you think I would be able to withstand that sort of weather when fishing...Wrong! When walking you are moving and if wearing the right gear, keeping warm and dry. When fishing you are static and when you are static you are not generating heat and so you start to chill, especially if you are wearing such things as cotton that does not wick the sweat from your body. Then there is wind chill, this is the big killer! If you do not wear garments that are not wind proof you will get cold pretty quickly, never mind the rain, its the wind that's the bad boy here!
When will folk learn? Cotton is one of the worse thing you could wear outdoors in bad weather AVOID!
I am not preaching to you all, but if you want to stay safe on the banks in winter (or summer!) then invest in some proper windproof/waterproof clothing! You do not have to by top of the range Goretex, you can get decent gear from your local Army stores cheaply these days. Try Silvermans army surplus on line, they have loads of gear to suit anglers...BUT, if you want gear that really works then invest in the Buffalo clothing system, still made in Sheffield for thirty years and trusted by special forces, mountain rescue and emergency services for many years! Take a look at their website and read the reviews, best bit of kit I have ever owned!