High end UnderArmor underwear.
Heavy Wool socks with Gortex boots, with at least 1200 grams of thinsulate insulation
Good coveralls with gortex and heavily insulated.
Good headgear and face masks.
Good gloves
Hand warmers and foot warmers
A portable small sportcat bottled propane heater for extreme cold.
Take blankets and extra clothes in case you fall in the drink and have to strip immediately
When you think you have on enough layers and have brought enough clothes put on and bring some more. You can't produce them if they aren't there but you can take them off if it get's to warm.
Call somebody and tell them where you will be and what time you will be back.