Fire Storm is a Master-levelDestructionspell that deals 100 base damage, hitting closer targets harder than those further away. Fire Storm unleashes an explosion of flames centered at the caster's location, immediately dealing high fire damage to all surrounding foes within range.
Like all Master-level spells, it requires both hands to cast, and takes some time to charge (around 4-5 seconds)
The charge up renders the Dragonborn immobile and vulnerable until cast or withdrawn. An easy solution is to use the Become Ethereal shout before casting. Another method is using dual casting Invisibility, wearing light armor, and/or using Muffle, then going in the middle of a crowd and casting it.
After charging, the Dragonborn can't cancel the spell by 'sheathing' (lowering) their hands. It is, however, possible to cancel the spell by going into the Magic section of the Inventory and deselecting the spell, or equipping another spell or weapon. This will work for spells or weapons selected from the character menu or from the favorites tab.
If staggered while using the spell, it cancels like any other spell.
Casting this spell in a confined space will cause all items to be blasted off of shelves. This could render a quest unfinishable, if a quest item is blasted to an unreachable location. If this happens, it may be possible to use the Alteration spell Telekinesis to retrieve the needed item.