The availability of hot water is so ubiquitos that it has become an important part of our life. We use hot water (sometimes as hot as boliling) to wash hands, brush teeth, shave, or wash utensils etc. It's ok to use hot (warm) water for shower or in winters but we are so much in habit that we do it in Summers as well.  Its not a necessity in summers, but a habit. Practice couple of days and you will realize you can actually live without hot water for most of the things.

You will save some on energy as well.

Anurag
PS: Water and warm water for shower are dream to many people in this world.