Responsa for Taanit 3:15

The second practice is that they customarily stop invoking and petitioning for rain on the first day of Passover, whereas it is well known that in Germany the sustenance of the produce is primarily from the rains that fall between Passover and Shavuot. The Mishna (Ta’anit 2a), which states that we stop [invoking rain] in the first day of Passover, was taught to the people of Eretz Yisrael, as I have demonstrated, and for them, the barley harvest was on Passover, and the wheat as well was already standing and only needed to dry out and ripen by Shavu’ot. Thus, rain was an omen of curse for them. But in Germany, where the produce cannot survive without the rain between Passover and Shavuot, [rain] portends blessing for them. So why should we not invoke and petition for rain until Shavuot? The laws of repeating [the Amida] for reciting “morid ha-geshem” [=the invocation of rain] will apply to them after Shavuot, just as it applies to residents of Eretz Yisrael from Passover on; as I have demonstrated, each land invokes and petitions for rain according to its needs. For just as Eretz Yisrael and Babylon have different practices for invoking and petitioning for rain, each according to its needs, so too other lands. For what is the difference? Further proof can be adduced from this (Ta’anit 14b): “The people of Nineveh asked of Rabbi [Yehuda the Prince]: Are those like us, who require rain even in the summer season, considered as individuals, who recite [the petition for rain] in “Shome’a Tefila,” or as a public, who recite it in “Birkat Ha-shanim”? He sent to them: You are like individuals, and [recite it] in “Shome’a Tefila.” They challenged [from a beraita]: “R. Yehuda said: When does this [cycle of fast days] apply? When the years are as ordained and Israel is settled on its soil. But nowadays, all depends on the year, and the locale, and the season.” You are challenging Rabbi based on a beraita? Rabbi is a tanna and disagrees!” Thus, we see that Rabbi only disagrees regarding the residents of a single city. However, regarding the land of Germany, which is very broad, Rabbi would agree that that they continue petitioning as long as they need rain, and since they petition out of need, they certainly invoke, for invoking also serves the petition. As R. Yohanan state: “As long as one petitions, one invokes.”