Leaves on my grape vines are getting dry and brown color. I water often. Last month vines looked nice and green but now they don"t look good. Maybe is too hot?
Check the vines for signs of insects or fungus disease. Treat with Neem Oil if you find any issues, and you may want to use as a preventative treatment.
Be careful to not water the leaves, if your needed to water due to dry conditions, water below.
Occasional drying leaves would not be uncommon as the late summer is upon us.
Review the growing conditions as in the link below.