First Bowl: Ugly and painful sores (16:2). Similar to the fifth trumpet of 9:1-11 and the torment of 14:10.
Second Bowl: Everything died in the bloody sea (16:3). Similar to, only more severe than, the second trumpet of 8:8-9.
Third Bowl: Rivers and springs became blood (16:4-7). Similar to the third trumpet of 8:10-11.
Fourth Bowl: The sun scorched people with fire but the people refused to repent (16:8-9). Somewhat the opposite of the fourth trumpet of 8:12.
Fifth Bowl: Beast's kingdom plunged into darkness.* People cursed God because of pains and sores, but they still refused to repent (16:10-11). Somewhat similar to fourth and fifth trumpets of 8:12 and 9:1-11. And perhaps a little like the sixth seal of 6:12-17.
Sixth Bowl: Unclean spirits call kings to Armageddon.** The unclean spirits are used to call Satan's people. This sounds somewhat like the opposite of the two witnesses, who were calling God's people.
"Behold, I come like a thief! Blessed is he who stays awake and keeps his clothes with him, so that he may not go naked and be shamefully exposed." (16:15). Sounds like some of the parables in the Gospels! Sounds as if God is telling his people to "hang in there" for a little while longer until He has destroyed Satan on earth.
Seventh Bowl: It is done! Lightning, thunder, earthquakes and hail are mentioned throughout the book of Revelation, but this is by far the most severe!
*Satan is often referred to as the prince of darkness!
**Frogs are mentioned in Exodus chapter 8 and Psalms 78:45 & 105:30. Frogs are called "...spirits of demons performing miraculous signs..." (16:14). Seems as if they are assembling (the Dragon, Leopard Beast, Lamb Beast, all the kings of the earth, false gods, apostate church) all in an alliance against God.
If the last 8 chapters of Revelation are an epilogue, then the bowls in chapter 16 must be during the harvest period in 14:17-20.