Yes this is true as in cold conditions our body doesn't feel the urge of water therefore we may become dehydrated not even knowing about it and of course in hot coditions we sweat therefore we loose water. Hope this helps :).
During winters, due to the cold weather intake of water by human beings is very less as compared to the intake during summer. Also, the intake small amount of water flushes out of the body in the form of urine.
As a result, our body gets dehydrated.
Whereas during summer's, intake of water is more and this water flushes out of the body in the form of sweat. As a result, we feel dehydrated and drink water again and again within some intervals.
