אורח חיים קי״דOrach Chayim 114

Se’if 1א׳

מַתְחִילִין לוֹמַר בִּבְרָכָה שְׁנִיָּה: מַשִּׁיב הָרוּחַ וּמוֹרִיד הַגֶּשֶׁם, בִּתְפִלַּת מוּסָף שֶׁל יוֹם טוֹב הָאַחֲרוֹן שֶׁל חַג, וְאֵין פּוֹסְקִין עַד תְּפִלַּת מוּסָף שֶׁל יוֹם טוֹב הָרִאשׁוֹן שֶׁל פֶּסַח.

The Laws of the Mentioning of the Wind and Rain and Dew. Containing 9 S'ifim We start to say "Who makes the wind blow and rain fall" in the second blessing in the Musaf prayer [i.e. Amidah] of the latter Yom Tov of "Chag" [the Sukkot-Shemini Atzeret holiday] (i.e. Shemini Atzeret), and we do not stop [saying it] until the Musaf prayer [i.e. Amidah] of the first Yom Tov of Pesach.

Se’if 2ב׳

אָסוּר לְהַזְכִּיר הַגֶּשֶׁם עַד שֶׁיַּכְרִיז שְּׁלִיחַ צִבּוּר וְיֵשׁ אוֹמְרִים שֶׁקֹּדֶם שֶׁמַּתְחִילִין מוּסָף מַכְרִיז הַשַּׁמָּשׁ מַשִּׁיב הָרוּחַ וְכו', כְּדֵי שֶׁהַצִּבּוּר יַזְכִּירוּ בִּתְפִלָּתָן, וְכֵן נוֹהֲגִין, (מָרְדְּכַי רפ"ק דְּתַעֲנִית). הִלְכָּךְ אַף אִם הוּא חוֹלֶה אוֹ אָנוּס, לֹא יַקְדִּים תְּפִלָּתוֹ לִתְפִלַּת הַצִּבּוּר, לְפִי שֶׁאָסוּר לְהַזְכִּיר עַד שֶׁיֹּאמַר שְׁלִיחַ צִבּוּר; אֲבָל אִם יוֹדֵעַ שֶׁהִכְרִיז שְׁלִיחַ צִבּוּר, אַף עַל פִּי שֶׁהוּא לֹא שָׁמַע, מַזְכִּיר; וּמִטַּעַם זֶה, הַבָּא לְבֵית הַכְּנֶסֶת וְהַצִּבּוּר הִתְחִילוּ לְהִתְפַּלֵּל, יִתְפַּלֵּל וְיַזְכִּיר, אַף עַל פִּי שֶׁהוּא לֹא שָׁמַע מִשְּׁלִיחַ צִבּוּר.

It is forbidden to mention rain until the prayer leader proclaims [it]. (And some say that before they start the Musaf prayer, the attendant proclaims "Who makes the wind blow, etc.", so that the congregation should remember [to say it] in their prayer, and that is how we practice (Mordechai on the beginning of the first chapter of [Tractate] Taanit)) Therefore, even if one is sick or has an extenuating circumstance [that prevents him from praying in the synagogue], one should not advance one's [Amidah] prayer [so it is before] the congregation's [Amidah] prayer since it is forbidden to mention [rain] until the prayer leader says [it]. But if one knows that the prayer leader proclaims it, even though one [oneself] did not hear it, one may mention it. And for this reason, the one came [late] to synagogue and the congregation had [already] started to pray [the Musaf Amidah], one should pray and mention [rain], even though one did not hear [the announcement] from the prayer leader.

Se’if 3ג׳

אִם אָמַר מַשִּׁיב הָרוּחַ בִּימוֹת הַחַמָּה, אוֹ לֹא אֲמָרוֹ בִּימוֹת הַגְּשָׁמִים, אֵין מַחֲזִירִין אוֹתוֹ; וְכֵן בַּטַּל, אִם הִזְכִּירוֹ בִּימוֹת הַגְּשָׁמִים, אוֹ לֹא הִזְכִּירוֹ בִּימוֹת הַחַמָּה, אֵין מַחֲזִירִין אוֹתוֹ. הַגָּה: וְאָנוּ בְּנֵי אַשְׁכְּנַז לֹא מַזְכִּירִין טַל, לֹא בִּימוֹת הַחַמָּה וְלֹא בִּימוֹת הַגְּשָׁמִים, רַק אוֹמְרִים בִּימוֹת הַחַמָּה וְרַב לְהוֹשִׁיעַ מְכַלְכֵּל חַיִּים וְכו'. (טוּר) יֵשׁ אוֹמְרִים שֶׁשְּׁלִיחַ צִבּוּר פּוֹסֵק לְהַזְכִּיר בִּתְפִלַּת מוּסָף יוֹם טוֹב הָרִאשׁוֹן שֶׁל פֶּסַח, אֲבָל הַקָּהָל מַזְכִּירִין וְאֵינָן פּוֹסְקִין עַד מִנְחָה, שֶׁשָּׁמְעוּ כְּבַר מִשְּׁלִיחַ צִבּוּר שֶׁפָּסַק בִּתְפִלַּת הַמּוּסָף, וְכֵן נוֹהֲגִין.

If one said, "Who makes the wind blow" (in the hot season) or if one did not say it in the rainy season, we make [that person] go back [and do it correctly]. And similarly regarding [saying] "dew", if one mentioned it in the rainy season or if one did not mention it in the hot season, we do not go back. Gloss: And we Ashkenazim do not mention "dew", not in the hot season and not in the rainy season; rather, in the hot season we just say "the Powerful One to deliver us. Sustainer of the living, etc..." [i.e. we do not mention dew in between those] (Tur). There are those who say that the prayer leader stops mentioning [rain] in the Musaf prayer on the first day of Yom Tov of Pesach, but the congregation does mention it [in Musaf]; and they do not stop until Mincha, for by then they already heard the prayer leader stop mentioning it in [the repetition of] the Musaf prayer. And that is how we practice.