Why do plant wilt in hot summer days

Because when the hot sun goes to the plants it's water instead of stay in the plant the sun takes it into the sky and then when the sun shines on the plant you are having Mega heat settle on the plant an because the plant has nothing to protect itself such as water it just dies because the mega heat killing the cells inside the plant that needs water while the heat is also burn up it nutrients that supports it.

Wilting occurs when the pace at which a plant leaves dispel moisture into the air.