Further proof of a post-tribulation rapture is seen in the study of the reoccurring phrase: "flashes of lightning, rumblings, and peals of thunder". If you don't already know, this phrase appears 4 different times in the Bible (all of which are in the Book of Revelation). It serves as a mutual point of intersection between 3 of those verses with the remaining verse telling us the significance behind the phrase itself.
That latter verse is found in John's vision of a Throne in Heaven, and is the first time we see this phrase used in the Book of Revelation. It reads:
Clearly, the person on said throne is Jesus, and the phrase "flashes of lightning, rumblings, and peals of thunder" is a descriptor of his physical appearance. That being said, when we see this same phrase used in the other 3 verses in the book of Revelation, we can understand that they, too, are signifying the physical presence of The Lord.
For example, when we read the description of the pouring out of the 7th bowl, we're told:
This clue clearly tells us that Jesus is physically present at this time, which we can agree on as it's commonly accepted that the 7th bowl marks the end of the Great Tribulation and return of Jesus to earth.
Yet, by no coincidence, this same phrase is also found in sounding of the 7th trumpet, as highlighted:
This not tells us that these two visions are undoubtedly connected (which is further evident by the fact that they both mention an earthquake and a hailstorm), but it also serves as a clue as to when the rapture of believers will take place. As I'm sure you're familiar with, when Paul was writing to the Corinthian church about the Resurrection of Life (i.e., The Rapture), he said:
Being that the 7th trumpet is the last trumpet of the series mentioned in Revelation and it marks the return of the Lord, we can confidently conclude that the rapture of believers takes place at the very end of The Great Tribulation!
Further detail about the rapture, the connection between the trumpets and the bowls of Revelation, and how God will protect His people from His wrath during the time of The Great Tribulation can be found in this article: The Great Tribulation and The Day of The Lord
That latter verse is found in John's vision of a Throne in Heaven, and is the first time we see this phrase used in the Book of Revelation. It reads:
“… there before me was a throne in heaven with someone sitting on it. And the one who sat there had the appearance of jasper and ruby. A rainbow that shone like an emerald encircled the throne. Surrounding the throne were twenty-four other thrones, and seated on them were twenty-four elders. They were dressed in white and had crowns of gold on their heads. From the throne came flashes of lightning, rumblings and peals of thunder…In the center, around the throne, were four living creatures…Whenever the living creatures give glory, honor and thanks to him who sits on the throne and who lives for ever and ever, the twenty-four elders fall down before him who sits on the throne and worship him who lives for ever and ever. They lay their crowns before the throne and say:
’You are worthy, our Lord and God,
to receive glory and honor and power, for you created all things,
and by your will they were created
and have their being.’” — Revelation 4:2b-5a,6a,9–11
Clearly, the person on said throne is Jesus, and the phrase "flashes of lightning, rumblings, and peals of thunder" is a descriptor of his physical appearance. That being said, when we see this same phrase used in the other 3 verses in the book of Revelation, we can understand that they, too, are signifying the physical presence of The Lord.
For example, when we read the description of the pouring out of the 7th bowl, we're told:
“The seventh angel poured out his bowl into the air, and out of the temple came a loud voice from the throne, saying, ‘It is done!’ Then there came flashes of lightning, rumblings, peals of thunder and a severe earthquake… From the sky huge hailstones, each weighing about a hundred pounds, fell on people...” – Revelation 16:17-18a,21a
This clue clearly tells us that Jesus is physically present at this time, which we can agree on as it's commonly accepted that the 7th bowl marks the end of the Great Tribulation and return of Jesus to earth.
Yet, by no coincidence, this same phrase is also found in sounding of the 7th trumpet, as highlighted:
“The seventh angel sounded his trumpet,… Then God’s temple in heaven was opened, and within his temple was seen the ark of his covenant. And there came flashes of lightning, rumblings, peals of thunder, an earthquake and a severe hailstorm.” – Revelation 11:15a,19
This not tells us that these two visions are undoubtedly connected (which is further evident by the fact that they both mention an earthquake and a hailstorm), but it also serves as a clue as to when the rapture of believers will take place. As I'm sure you're familiar with, when Paul was writing to the Corinthian church about the Resurrection of Life (i.e., The Rapture), he said:
“Listen, I tell you a mystery: We will not all sleep, but we will all be changed — in a flash, in the twinkling of an eye, at the last trumpet. For the trumpet will sound, the dead will be raised imperishable, and we will be changed.” — 1 Corinthians 15:51–52
Being that the 7th trumpet is the last trumpet of the series mentioned in Revelation and it marks the return of the Lord, we can confidently conclude that the rapture of believers takes place at the very end of The Great Tribulation!
Further detail about the rapture, the connection between the trumpets and the bowls of Revelation, and how God will protect His people from His wrath during the time of The Great Tribulation can be found in this article: The Great Tribulation and The Day of The Lord