It doesn't appear to go any deeper than the skin.

Sunscald.

I agree, it turned too hot suddenly and the apple couldn't adjust. Provide some 40-50% shade cloth if possible.

Thanks guys that's exactly what it is, after researching it. The weather is cooling down and will actually be cloudy the next few days, supposedly, so I think I will be fine. The tree had too many apples anyways it is probably good that some got "pruned" off. I should purchase some 40-50% shade cloth for the future though since I don't have any on hand. California weather seems to love going from extreme to extreme. Where can I buy it? Is it common? Thanks!

It's funny, I was excited for the heat because I thought it would stop any powdery mildew that may want to ruin my grapes, but instead it ruined 1/4 my apple crop!

My tree says thanks! I'll know how to protect it next time (;

I believe it is bitter rot, looks like the V-shaped pattern is forming where the damage appears.