Taanis 1:1-2

Taanis 1:1

When do we start mentioning the power of rain in Shemoneh Esrei? Rabbi Eliezer says from the first day of Succos but Rabbi Yehoshua says from the last day. Rabbi Yehoshua said to Rabbi Eliezer, "Since rain on Succos is considered a sign of God's displeasure with us (in that it prevents us from fulfilling the mitzvah of dwelling in the succah), why should we pursue it?" Rabbi Eliezer replied, "I didn't say we should ask for rain, merely to acknowledge it in the form of 'He makes the wind blow and the rain fall' - i.e., in the proper time." Rabbi Yehoshua responded, "If that were the case, we should 'mention' it all the time!" (In other words, there is an implied request.)

Taanis 1:2

We do not ask for rain unless it is near the rainy season. Rabbi Yehuda says that the one who leads the musaf service on Shemini Atzeres mentions rain but the one who leads shacharis does not. On the first day of Passover, the one who leads shacharis still mentions rain but one who leads musaf does not. Until when do we pray for rain? Rabbi Yehuda says until after Passover and Rabbi Meir says until the month of Nisan has ended as per Joel 2:23, "He will cause rain to descend for you, the early rain and the late rains in the first month."