Well if you think it is very cold, if you can't take the cold weather then the your Guinea pigs feel the same. You'd have to give them some blanket. Make them feel warm and cozy where ever they are. Make a little run inside with newspapers and blankets. This will make them feel comfortable.
Guinea pigs can get cold just like you. Maybe you could make a little nest for him/her to sit it out of an old towel or blanket.
Yes and the number one way is if you clean out their cage and don't dry it completely! Damp cages can lead to a cold, bronchitis or even pneumonia! If a guinea pig is cold period, it may catch a cold. Visit www.cavysprit.com for lots of information about these pets.