Scalp chaffing

[Thinking1]

Switched to aveno pure renewal shampoo with seaweed extract about 6 weeks ago. Liked the way it left my hair and sulfate free. Yesterday after shower noticed the front of my scalp peeling, flakin. Kind of looks like scaly. Noticed more flakes of dead skin in hair also. Not sure if this is a reaction to the shampoo after 6 weeks or just due to more exposure to sun. Was really hot last two days, was outside some, but wore a hat most of the time I was in the sun. Should I chalk the scalp irritation up to the weather or switch back to old shampoo?