Conditioners contain moisturizer that are designed to stay in your hair. But if you rinse your hair with hot water all the conditioner will rinse out. That's why professional stylists rinse conditioner with cool water, so the moisturizer will stay in your hair. But no warm or hot water won't damage your hair unless of course it's so hot it causes injury like burns. But I think if you were burned your hair would be the last of your worries.