On the Jewish liturgical calendar, a one-line prayer for rain is replaced on Passover with a prayer for dew. David Wolpe explains the significance of this seasonal shift:
[I]n Israel the time for the grain harvest [begins on Passover], and if the winds blow and the rains fall, the grain cannot be harvested and will rot in the field. Dew, on the other hand, will moisten the grain without damaging it. That simple change in the prayer marks a profound truth about Judaism that touches on modern politics as well. . . .
[Throughout history], Jews all over the world prayed for rain or dew when it was needed in Israel, no matter where they lived. The assumption of Jewish history is that they would soon be back in Jerusalem. . . .
Such practices remind us [of] a deep truth about Judaism—it is a 3,000-year-old love affair with a land. . . . For generations, Jews in every corner of the globe prayed for the land they had never seen, that many would never see.
Read more on Time: http://time.com/4306874/passover-prayer-and-israel/