There is no imminent threat to the UK that has been disclosed.
When I lived in Tillicoultry in Scotland some 50 years ago we had a 'snow pantry' because getting snowed-in for a week wasn't uncommon in the Winter. Build it up over Summer and use it if you need it. This is the same thing.
This appears to be deeper than what you are implying and possibly to do with Russia's hybrid warfare / AI. Unfortunately we only have vague statements to work with from the Prime Minister.
Burnham added: "It's not about panic buying... It's about just taking sensible measures to have enough in the house to tide you over should there be a difficult situation."
Speaking at a wildfire resilience summit in Liverpool, Burnham denied the government had failed to properly prepare, saying: "No, we're having the conversation with people about being better prepared because we're living in a world where unexpected events seem to be becoming more and more common.
"Obviously, weather events, and we're in a situation today where the UK is facing storms and obviously, we feel for the people without power in Cornwall right now.
I'm absolutely sure there's an undercurrent of "Russia might..." but with at least my house being battered by 50+mph winds coming off the Atlantic right now, I think the more realistic threat is flooding/wind-damage etc.