I mentioned how easy it would be to make a "Rain of" spell for electricity when I was talking druid spells. Here it is:
Rain of Lightning
Miniature bolts of lightning rain from the sky into the area of effect, causing 1d-1 burning damage to all within it. Metal armor provides only DR 1; other armor protects fully. Creatures under the Rain of Lightning take damage on their own turns; halve damage (round down) if less than a full second is spent in the area of effect. Wooden shields may be held overhead as described under Rain of Fire (Magic p. 74); metal shields provide no protection! This spell can only be cast outdoors.
Duration: 1 minute.
Base Cost: 1 to cast (minimum 2). Same cost to maintain. For double base cost, the Rain of Lightning does 2d-2 per second.
Prerequisites: Magery 2 and Lightning.