19 God’s temple that is in heaven was opened, and the ark of the Lord’s covenant was seen in his temple. There followed lightnings, sounds, thunders, an earthquake, and great hail.
And the temple of God…was opened – see also Rev 7:15; Rev 21:3. This may have the meaning of Joel 2:32, “whoever calls on the Name of the LORD will be saved,” in the final day. In Rev 15:8, we are told that the no one was to enter the temple until the seven plagues were finished. Rev 21:23 tells us there is no temple after the Lord’s Day. The reason is described in Rev 7:15 and Rev 21:3, “now is the dwelling of God with men.”
and an earthquake and a great hailstorm – described under the seventh bowl of wrath, in Rev 16:17-20.