This spell enables the caster to harness a non-magical wind and change its force by one rank, as shown on Table 79, “Weather Conditions,” in the DMG. For example, “becalmed” conditions (those found on a still day) can become a light breeze. A light breeze can be diminished to becalmed conditions or increased to a favorable wind.
The spell works equally well in an enclosed area, such as a dungeon, where “wind conditions” are considered becalmed. Wizards of the 9th level or less can modify only natural winds of storm force or less. They can increase a storm-force wind to gale-force, but cannot affect an existing gale-force wind. At 10th level, a wizard can alter gale-force winds, and at 15th level, he can reduce hurricane-force winds. The change caused by this spell is immediate, with the area of effect centered on the caster. He can alter the wind only once (which means by one level only). As long as a wind is shaped by this spell, subsequent alter wind spells cannot affect the same area. Other magics that change wind or weather can affect an altered wind, however. When the alter wind spell ends, the air returns to its original state.
Alter wind has no effect on creatures of elemental air. Nor does it affect creatures that use air in their attacks. The wind cannot deflect an enemy's breath weapon and send it back toward the attacker, for example. However, alter wind does enable the caster to move non-magical fog, dust, or poisonous gas out of his way, negating its effects for 1d6 rounds.
The spell requires a small silver tube, through which the caster blows to attract the wind's attention.
Notes: Common in Arabian settings; otherwise rare.