Wikipedia
The concept of a Prewrath rapture is one of several premillennial views on the end-times events among some evangelical Christians, and states that Christians will be raptured at the end of a time called the Great Tribulation (which begins at the midpoint of the seventieth week of Daniel), and before the Day of the Lord. (God's wrath). The prewrath position emphasizes the biblical distinction between Satan's wrath in the Great Tribulation (which Christians have been promised) and the wrath of God (which Christians have been promised deliverance/salvation from).
According to the Prewrath perspective, the great tribulation begins 3.5 years after the Antichrist "makes a covenant with the many" ( Daniel 9:27), in the middle of "Daniel's 70th week." The 70th week is a reference to Daniel 9:24, where each day of the week corresponds to a year (for a total of seven years). After the first 3.5 years, the Antichrist will make himself known with the abomination that causes desolation, and he will reign for 3.5 years (42 months or 1260 days). The latter half of the 3.5 years is characterized by the Antichrist deceiving the world and persecuting the church.
Although the exact timing of the rapture is not known, one of the key points to the Prewrath view is that the rapture comes after the sixth seal is opened (Revelation 6:12), when the moon is turned into blood. The tribulation of God's people will then be cut short (according to Jesus in Matthew 24:29-31, Mark 13:24-27) with the second coming of Christ and the rapture, and those who are left behind on Earth will face the trumpets and bowls of God's wrath (Rev 16:1); hence the term "Prewrath."
God's wrath against the ungodly will follow for the remainder of the seven years in what is known as the Day of the Lord.