What happens if a person doesn't drink enough water in winters?

Dr Rahul Mathur, from CK Birla Hospitals, said low water intake can cause winter dehydration. He said, "Low temperatures reduce...thirst response by up to 40%. Simultaneously, we lose fluids through dry indoor heating, faster breathing in cold air." He said even mild dehydration can cause fatigue, adding that low fluid intake “thickens blood, raising risks of hypertension".