Former international Folau, who is a Christian, said: "Look how rapid, these bushfires, these droughts, all these things have come, in a short period of time.
"You think it's a coincidence or not?"
Folau told the congregation that the same-sex marriage and abortion laws went against "God's word" and the country needed to repent.
Six people have died in the fires which have caused devastation across parts of the country.
Prime Minister Scott Morrison criticised Folau for his sermon, telling reporters on Monday: "He is a free citizen, he can say whatever he likes but that doesn't mean he can't have regard to the grievance [and] offence this would have caused to the people whose homes have burnt down."
Folau is currently trying to sue Rugby Australia over his sacking, after he was dismissed for claiming that "hell awaits" homosexuals.