How does a sheep's fleece impact its tolerance for high temperatures?
Wool serves as a good insulator, meaning it doesn't allow warmth to escape the wearer easily allowing the wearer to remain warm. Furthermore, wool helps maintain a dry environment by absorbing moisture from the air (and sweat) which can also keep you cool during summer.
Here's a link that talks more about this for both wool wearers and sheep: https://shepherdsdream.com/blog/wonders-of-wool/how-wool-keeps-us-cool/