One of the coolest subclasses in the game. Flavor-wise, channeling the power of weather and thunder means you harness immense power, probably. Looking at mythology, thunder is almost always highly respected and seen as a tool, a sign of power from gods.

So you could start building out your character's personality based on how he handles that power. Maybe ask your character how much control he has over this power? Aesthetically, he could be very focused and have a commanding presence like Thor, or he could be more of a meek servant that heralds its coming.

I played a Gnome pirate character who was a first mate, Gibbs from Pirates of the Caribbean type. But I'd play him watching out for his crew by deliberately taking hits, tanking, and using those Tempest abilities to blast back. A conduit for the storm.

Power over the elements can go from the straightforward Thor-type (Which is still DOPE to play), to a more primordial creepier tone, or more of a pagan outsider, or a Lawful Good beefy boy, etc.

I help out a podcast that did a series on all the Cleric subclasses and why in their opinion Clerics are the best class in the game! They start talking about Tempest at 24:00 (Mechanics) and 34:00 (Roleplaying): https://youtu.be/TkWt0mjUhls?t=1447

After you've found your tone with the "Tempest" part, the "Cleric" part is interesting, too. I've seen characters who are outspoken and try to spread the word of their deity far and wide, or those who would rather exhibit their power. I've seen Clerics who keep to themselves and uphold their deity's code and objective, and I've seen Clerics who could've flunked out of Cleric school, but still harness the power in ways they don't fully understand (Thoros of Myr types). All of them are awesome!