War Weather Lorebook

Bring this to Neidir’s attention immediately. It’s a transcript of an old text, but she needs to see this. Beg her pardon the conjecture on Nordic legends and Psijic nonsense, but this text contains the angle of attack she was looking for:
Weather magic has never been an exact science, perhaps because of the temperamental nature of what it seeks to control.
Minor spells to conjure gusts of wind or forks of lightning are common, but manipulation of a region’s climate is much more difficult to achieve. I imagine that our war wizards have dreamed of lowering catastrophic hailstorms onto enemy borders as a preamble to invasion, or halting a blizzard to make an unexpected march through inclement weather.
There are claims to such spells originating in foreign lands and beyond.
Legend has it that a sect of Nords in faraway Skyrim command the spell-like language of dragons, which allowed them some mastery over the weather. Accounts of these Nords’ abilities during the Merethic Era Dragon War include the power to diminish fogs, mists, and clouds with the sheer bravado of their shouts. Negil’s "Dragons at Windhelm" notes that an army of these bellowing Nords foiled an airborne sneak attack by dragons who sought to strike under a cover of storm clouds. Negil writes, "We desired the heavy clouds parted, and when we spoke our Words of Power, the clouds thought so, too. But even with their passing, the sun remained hidden. A now-apparent wing of dragons stretched across the heavens for miles, and the curse that escaped Vofodor’s mouth brought a hearty guffaw to mine. Our Words of Power did not spare us the battle, but they told us battle was coming. And we joined it gladly."
Far to the south of Skyrim, members of the Psijic Order have been long-rumored to possess spells cast in the Old Way of magic that can bend the elements to the user’s desire. Our scouts have reported sudden storms and flash rain off the coast of Artaeum for years. Unfortunately, the Psijics never left instructional texts to find.
Arresea’s "The Daedric Primer" describes a spell devised by Sheogorath, Daedric Prince, called Manipulate Weather. She writes, "Sheogorath’s spell folio includes an incantation to match the weather with his mood. The Lord of the Madhouse has been known to teach the spell to mortals in his favor, allowing them to alter the climate of an entire region. Unfortunately, the spell functions at Sheogorath’s whim, no matter who casts it—meaning it functions entirely randomly. There are stories of his followers trying to stymie flashfloods but summoning torrential rain instead, or trying to put out brush fires and feeding them with unwanted lightning storms, to Sheogorath’s delight—and theirs.
I include the above examples to say that large-scale weather control has been noted across the ages, and that weaponizing such an ability would be an incredible asset to the Maormer military. I set out to prove as much this past winter, with the help of twenty journeyman mages. We cleared an open plain in the jungle and prepared to create a lightning storm by manipulating the charge of a passing cloud with our own skeins of lightning. For a moment, we succeeded, unfortunately losing a member of our group in the sudden storm and wayward lightning. It’s possible we would all have perished—entirely regrettable—had our storm not consumed itself. We tried sseveral more times, managing to lengthen the duration of the storm each time, even learned to direct it out over the water. But the storm duration remained our enemy, and we eventually had to admit that the exercise would be futile in a battle. If, however, we had had some way to physically suspend our spell at a high altitude—perhaps a device? A series of devices—would eliminate the need for continued expenditure of magicka and free the casters to direct a storm across a great distance.