Ohh all this talk of winter! I was planning on sticking my head in the sand about it for a while longer.....
If you ride on fields, mark any badger-type holes with marker posts so you know where they are in the snow
I have just bought a pair of thermal jodhpurs from kerrits - they promise fabulous results
I bought a bit warmer from a member of this forum and do recommend it.
Bring your tack cleaning products inside; they'll freeze solid if your tack room is unheated!
Make sure you have one working, and one spare water heater to float in the water trough
Thin gloves and thick gloves - layers work on fingers too
Remember that when it does go below -20 you should not be working the horses too hard because drawing in air that cold into their lungs is damaging and can cause problems long term. So the colder it gets.... the steadier you need to be.
Umm that's all I can think of right now but...thanks for reminding me that it's just round the corner