Gewitterwolke
Gewitterwolke is a ninth level conjuration with a range of sight, a duration of a minute, and requires concentration to maintain.
Gewitterwolke causes the rapid formation of a cumulonimbus cloud above the open ground. Below the cloud, in a radius of about three hundred and sixty feet, rain may fall, and the wind will blow. If a second instance of the spell is cast before the first ends, the ph of the rain lowers to about 3.5, which is less acidic than vinegar. After a third instance, lightning increases significantly. After a fourth casting, hail begins to fall as large as a golf ball. The fifth casting will produce freezing rain and winds up to fifty miles per hour, making concentration difficult. When the spell ends, all water and hail produced fades into mist.
Gewitterwolke was discovered in Germany in 1891. Since then, nations around the globe have tried to make the spell viable for irrigation. Australia worked extensively from 1947 to the 1960s, and the United States held an experiment as recently as 2006 in Wyoming to examine the effects on snowfall. The most massive experiment ever conducted was in February 2009 in China. With a mix of technology and magic, snow began to fall in Bejing and lasted for approximately three days and led to the closure of twelve main roads. Later, in October, China recorded its earliest snowfall since 1987.
The most common use of the spell is in the aviation and maritime training industries.