By means of a control winds spell, the caster is able to alter wind force in the area of effect. For every three levels of experience, the caster can increase or decrease wind force by one level of strength. Wind strengths are as follows: Wind Force Miles Per Hour Light Breeze 2-7 Moderate Breeze 8-18 Strong Breeze 19-31 Gale 32-54 Storm 55-72 Hurricane 73-176 Winds in excess of 19 miles per hour drive small flying creatures—those eagle-sized and under—from the skies, severely affect missile accuracy, and make sailing difficult.
Winds in excess of 32 miles per hour drive even man-sized flying creatures from the skies and cause minor ship damage. Winds in excess of 55 miles per hour drive all flying creatures from the skies, uproot small trees, knock down wooden structures, tear off roofs, and endanger ships. Winds in excess of 73 miles per hour are of hurricane force.
An "eye" of 40-foot radius, in which the wind is calm, exists around the caster. Note that while the spell can be used underground, if the spell is cast in an area smaller than the area of effect, the eye shrinks 1 foot for every foot of confinement. For example, if the area of effect is a 360-foot area, the eye shrinks by 10 feet to a 30-foot radius; a space under 320 feet in a radius would eliminate the eye and subject the spellcaster to the effects of the wind. Once the spell is cast, the wind force increases or decreases by 3 miles per hour per round until the maximum or minimum speed is attained. The caster, with one round of complete concentration, can stabilize the wind at its current strength, or set it to increase or decrease. However, the rate of the change cannot be altered. The spell remains in force for one turn for each level of experience of the caster. When the spell is exhausted, the force of the wind wanes or waxes at the same rate, until it reaches the level it was at before the spell took effect. Another caster can use a control winds spell to counter the effects of a like spell up to the limits of his own ability.