
Natural storms range in size from a small cell to a very large storm that stretches across many miles.

(And so on for ten minutes or until spell concentration ends). As each turn passes, the caster is not constrained by location and could do this: The spell is cast and down comes the first stroke of lightning. There's a storm cloud already there because we have stormy weather. Under such conditions, the spell’s damage increases by 1d10. If you are outdoors in stormy conditions when you cast this spell, the spell gives you control over the existing storm instead of creating a new one. The rules don't constrain the spell caster to standing in place while concentrating on the spell while she calls down lighting. The tweet is a terse dev ruling that the conjured storm cloud stays in the spot where it was created (the rules don't specify that) and does not move with the spell caster. You can call down lightning once per turn on any target within range(120').

In the first there is no natural storm to get lightning from, so the spell caster conjures one with modest dimensions: a 10' tall cylinder with a radius of 60' that begins 100' above the head of the spell caster. Based on this question, and a tweet from Mike Mearls in this answer: how flexible is the second form of call lightning for the spell caster?Ĭall Lightning has two forms.
