How do they know when God is angry?

[Believe Heart]

How do religious people know when God is angry, or maybe happy or horny? But they usually claim he is angry.

How do you know when your mother is angry with you?
I am pretty sure that even while you're still doing things, you know perfectly well if it's something that will piss your mother off.
That is how we know it.
From his words and actions (on earth) we learn God's personality.
Btw God has love more than your mom when you are a good boy, however,
How would your father feel about you if he found out you were a serial killer? How much would he hate you?

Whether God is full of love or hates towards you is entirely in your hands.