Cloudburst is a level 3 spell from the Priest Scroll in Icewind Dale, which was added with Heart of Winter.
For the purposes of this spell, "cold- and fire-dwelling creatures" is any creature whatsoever (friend or foe) who has cold and/or fire resistance at 100% or above. So that part of the spell affects, for example, most undead creatures in the game (due to them having 100% cold resistance).
This spell is also not party-friendly (though, once again, the first part of the effect won't affect party members unless they have 100% or above cold and/or fire resistance).
Description[]
| “ | This spell brings forth a magical rain that saturates the area of effect. All cold- and fire-dwelling creatures take 2d3 points of magic damage per round. In addition, all creatures in the area have a 50% chance per round of being struck by bolts of lightning that deal 2d6 electrical damage, with a Save vs. Spell for half. Flame Blade, Shroud of Flame, and salamander auras are extinguished by Cloudburst. | ” |