There is a passage in the book in which the warnings sent by God to Israel are described. The judgement prophesied by Amos is not coming without warning, but only after a long time of patient waiting on the part of God.

4: 6 -12 describes warnings sent by God, in the form of drought and famine, dry winds, locusts, plague, war and earthquake. In Deuteronomy 28 such disasters were understood to be punishments sent by God for disobedience to him. These things had taken place in Israel but the Israelites had not seen what they signified.

That God had longed for Israel to turn back to him is clear from 5: 4-6: 'The Lord says to the people of Israel, "Come to me, and you will live ... ".' Chapter 5: 14-15 reinforces this. The first two visions of Amos indicated that God had given Israel time to repent.