Weather summoning

By using the weather summoning spell, the caster calls forth weather appropriate to the climate and season of the area he is in. The summoned weather is not under the control of the caster. It might last but a few minutes, in the case of a tornado, or for hours or even days in other cases. The area of effect likewise varies from about 1 square mile to 100 square miles. Note that several casters can act in concert to greatly affect weather, controlling winds, and working jointly to summon very extreme weather conditions.

Within perhaps a half-hour after the spell is cast, the trend of the weather to come is apparent--e.g., clearing skies, gusts of warm or hot air, a chill breeze, overcast skies, etc. Summoned weather arrives one to three hours after the spell is cast. Note that the new weather condition cannot be changed by the caster once it has been summoned. Once the weather is fully summoned, it cannot be dispelled. If the summoning is successfully dispelled before it has been completed, the weather slowly reverts to its original condition.

Note: This version of weather summoning originally appeared in the 2nd Edition Player's Handbook for Advanced Dungeons & Dragons from TSR. Its use here is for the purposes of providing context for the campaign only.