כִּ֡י כַּאֲשֶׁ֣ר יֵרֵד֩ הַגֶּ֨שֶׁם וְהַשֶּׁ֜לֶג מִן־הַשָּׁמַ֗יִם וְשָׁ֙מָּה֙ לֹ֣א יָשׁ֔וּב כִּ֚י אִם־הִרְוָ֣ה אֶת־הָאָ֔רֶץ וְהוֹלִידָ֖הּ וְהִצְמִיחָ֑הּ וְנָ֤תַן זֶ֙רַע֙ לַזֹּרֵ֔עַ וְלֶ֖חֶם לָאֹכֵֽל׃
Sebab seperti hujan dan salju turun dari langit dan tidak kembali ke sana sebelum membasahi bumi, membuatnya melahirkan dan bertunas, serta memberikan benih kepada penabur dan roti kepada orang yang makan,
Shulchan Arukh, Orach Chayim
8. All this order applies when there is no rainfall at all, but if rain falls in the fourth part [of the rainy season (the term 'the fourth part' refers to the rain that falls to stimulate the growth of every plant and herb of the earth. It is called 'a quarter' because it penetrates and goes beyond the ground, as it is written, 'For as the rain comes down, and so on, and gave seed to the sower and bread to the eater.) when the herbs sprout and begin to wither, they fast and cry out until rain falls or until the plants dry up. Similarly, if the time for Passover arrives or is approaching, which is the time of the blossoming of the trees in the Land of Israel, and there is no rainfall, these individuals fast and cry out until suitable rain falls for the trees, or until their season passes. Similarly, if the festival of Sukkot arrives, and there is not enough rain to fill the cisterns, pits, and caves, they fast until the appropriate rain for filling them falls. And if they do not have water for drinking, they fast for rain at any time when they do not have water to drink, even during the hot days. If there is a break in rainfall between one rain and another for 40 days, it is considered a drought. They fast, cry out until rain falls, or until their season passes.