It's more than just temperature though .
They need to have constants of temperature , don't bring them from cold-warm or put them from warm-cold .
They need to be dry . Damp can kill them. And draughts .
They are more likely to cosy themselves in their bedding so it needs to be dry , fresh plentiful hay . You might find he just hides rather than enjoy fresh air 
You can put a cover (clean plastic so it gets light) over the hutch to give him protection from damp and draughts . Anchor it slightly away from the front so there's ventilation.
SnugglePads (solid microwaveable plastic disc) wrapped in the fleece cover or newspaper , buried in the hay .
My pigs had a wooden playhouse with floor level hutches opening onto floorspace .
They were fine in the shed till about November then came in for Guy Fawkes and we played it by ear .
When they went out , I put fresh bedding (room temp) Snugglepads and a small heater for 30minutes . Then they went to their shed .
Out first two pigs (brothers) needed space and tolerated their indoor cage grudgingly .
Our neutered boar and his two wives didn't mind it (only for sleeping )
If you want a long term indoor , C&C is more versatile , I made huge cages when mine got older and we kept them indoors all winter .
How old is your piggie ?
Is this his first winter with you?
Has he had a cagemate ?
We had our last pig alone from Jan-April (when her companion died till she died) she was in our small bedroom and spent most of her time with DD.