Cats and dogs can be thirstier in warm weather, after exercise or salty treats, just like us. However, if their daily water intake has increased significantly then they could have an underlying health concern. Some causes of increased thirstiness in older pets include kidney disease, liver disease, infections such as urinary tract or uterine infections, and hormonal disorders such as diabetes and hyperadrenocorticism. Your pet should be examined by a vet, who may also test your pet’s blood and urine to figure out what is going on.