Harry's face turned red and he started to yell, balling his hands up into shaking fists.

What can we infer about Harry's mood?

He was becoming frustrated or angry.

Explanation:

People's faces will turn red when upset, as the blood rushes to their faces. Yelling also indicates that he is no longer calm, meaning he is probably frustrated. Balling his hands into fists is a coping method some people use when they becomes upset, as it gives them something to squeeze or release energy into.