On the Festival of Shemini Atzeret, the musaf service begins with a special prayer for Rain (geshem). From that time, and throughout the winter months, until the first day of Passover, we say in the Amidah (in the second blessing, called gevurot —mighty acts, the words, Mashiv haruach umorid hageshem, — Who causes the wind to blow and the rain to come down. On the first day of Passover a similar prayer is recited for Dew ("Tal"), and from the first day of Passover, throughout the summer months, the words mashiv haruach, etc., are omitted, and in some congregations supplanted by the words morid hatal, —Who causes the dew to come down.

The Prayer for geshem on Shemini Atzeret (as the Prayer for Tal on Passover) is an impressive one. The cantor puts on a white kittel, and recites the prayer in a solemn tune reminiscent of the Solemn Days.

The reason for these special prayers is understandable enough. The winter months in the Holy Land are the Rain Season, and the entire life of the country depends on rain. If the rains come down in their due season and in sufficient quantity, the rich soil will produce abundant crops and fruits; if not, the country is doomed to famine and starvation.

During the summer months there is no rain; it's the dry season. During these rainless months, the earth would have been completely parched, the top soil would have turned into dust and would have been blown away by the wind; the land would have turned into barren desert were it not for the dew which settles on the cool soil during the hours of the night, drenching the ground with the soft moisture which we know as dew, and which sparkles in the early rays of the sun like pearls.

Thus, the rain in the winter, and the dew in the summer, are vitally needed to sustain life. And since we Jews recognize that it is G‑d, the Master of the world, who is the Master over the wind and clouds, who makes it rain whenever and wherever He desires, we turn to G‑d with our prayers for rain and dew in their proper seasons: Geshem on Shemini Atzeret, at the beginning of the winter season; Tal on the spring festival of Passover, at the beginning of the summer season.