The fire of the Lord in the Old Testament consumed the disobedient. This is a foreshadowing of the wrath to come for all those who reject Jesus Christ.
In today's world with the outpouring of the Holy Spirit, people will often feel heat when the power of God comes upon them. For those who humble themselves, this heat is a cleansing fire.
Old Testament fire:
When you appear for battle, you will burn them up as in a blazing furnace. The Lord will swallow them up in his wrath and his fire will consume them. - Psalm 21:9
New Testament fire:
His winnowing fork is in his hand, and he will clear his threshing floor, gathering his wheat into the barn and burning up the chaff with unquenchable fire.” - Matthew 3:12