Guinea pigs should not be kept outside during the cold, wet months as they are very susceptible to the damp. Remember that they originate from South America, and their little bodies are not adapted to the cold, damp weather of northern Europe.
Their accommodation should be either indoors or at the very least in a shed or outbuilding. There is every possibility that during really cold periods of weather, your guinea pig will perish if he is not adequately protected from the weather, so please give serious thought to this aspect of his care.
If your guinea pig is old and/or has respiratory problems then you should seriously consider moving them indoors for the winter. On more than one occasion we have brought an older guinea pig indoors with laboured breathing due to the damp, cold winter weather. On every occasion their respiration has improved.
The British winter doesn’t just mean cold weather and, as we have seen this year during the January and February storms, during adverse weather conditions an outside hutch can be severely damaged by high winds by being flipped over. They are usually made of softwood and are often found smashed to pieces. When this happens, the guinea pigs are usually never seen again. Please bear in mind the weather forecast and, if storms are likely, get your guinea pigs indoors to safety! Better still, make sure they are housed inside at all times during the winter, and safe from any risk.