[Taqwus]

Staff of Storms, 2-hd weapon, requires Air-3 and thus 20 gems, was Cons-6 (but may be Cons-4 post-patch? Need to check). Causes storms and can be used to cast lightning bolts. The 2-hd unique sword Tempest also causes this, and permits a Thunderstrike cast per action, but is harder to forge being unique and air-4.
Yes, it'll hurt precision, although you might be able to compensate somewhat with Wind Guide. However, if you can get lightning immunity, something like Wrathful Skies is potentially rather deadly.