Anger is not a sin; it is a God-given, God-experienced emotion. Sin enters when our response to the felt emotion goes against showing respect and dignity to image bearers, such as ourselves. 

God experiences anger when Israel continues to return to idol worship and disobedience to their covenant (i.e., God’s boundaries he set up for the Israelite people to protect their relationship with Him and themselves). There are consequences to pushing against God’s boundaries such as distance from Him (i.e. Genesis 3:23-24). Many times in the Old Testament, we see God distance himself from the Israelites when they do not keep the covenant. However, He does not ever cease to offer an alternative response that would lead to restoration of the relationship.