Gen. 6:6 And it repented the LORD that he had made man on the earth, and it grieved him at his heart.
2 Kings 20
1 In those days was Hezekiah sick unto death. And the prophet Isaiah the son of Amoz came to him, and said unto him, Thus saith the LORD, Set thine house in order; for thou shalt die, and not live.
2 Then he turned his face to the wall, and prayed unto the LORD, saying,
3 I beseech thee, O LORD, remember now how I have walked before thee in truth and with a perfect heart, and have done that which is good in thy sight. And Hezekiah wept sore.
4 And it came to pass, afore Isaiah was gone out into the middle court, that the word of the LORD came to him, saying,
5 Turn again, and tell Hezekiah the captain of my people, Thus saith the LORD, the God of David thy father, I have heard thy prayer, I have seen thy tears: behold, I will heal thee: on the third day thou shalt go up unto the house of the LORD.
6 And I will add unto thy days fifteen years; and I will deliver thee and this city out of the hand of the king of Assyria; and I will defend this city for mine own sake, and for my servant David's sake.
Jonah 1
1 Now the word of the LORD came unto Jonah the son of Amittai, saying,
2 Arise, go to Nineveh, that great city, and cry against it; for their wickedness is come up before me.
Jonah 3
1 And the word of the LORD came unto Jonah the second time, saying,
2 Arise, go unto Nineveh, that great city, and preach unto it the preaching that I bid thee.
3 So Jonah arose, and went unto Nineveh, according to the word of the LORD. Now Nineveh was an exceeding great city of three days' journey.
4 And Jonah began to enter into the city a day's journey, and he cried, and said, Yet forty days, and Nineveh shall be overthrown.
5 So the people of Nineveh believed God, and proclaimed a fast, and put on sackcloth, from the greatest of them even to the least of them.
6 For word came unto the king of Nineveh, and he arose from his throne, and he laid his robe from him, and covered him with sackcloth, and sat in ashes.
7 And he caused it to be proclaimed and published through Nineveh by the decree of the king and his nobles, saying, Let neither man nor beast, herd nor flock, taste any thing: let them not feed, nor drink water:
8 But let man and beast be covered with sackcloth, and cry mightily unto God: yea, let them turn every one from his evil way, and from the violence that is in their hands.
9 Who can tell if God will turn and repent, and turn away from his fierce anger, that we perish not?
10 And God saw their works, that they turned from their evil way; and God repented of the evil, that he had said that he would do unto them; and he did it not.
It sure seems to me that He can change His mind, if He chooses to do so.