How to get to Tempest Temple
The fastest way to reach Tempest Temple is by taking the Guild Hall portal to Katta Castrum: Deluge. Once you zone in you'll find the zoneline to Tempest Temple just south of where you are, on the other side of the large stone platform.
In order to zone into Tempest Temple you will want to walk ontop of the pyramid shaped platform. There's a round glowing circle atop that you step on to be transported to Tempest Temple.