On Pesach we switch from mentioning rain in the Amidah to speaking of tal, dew. Instead of adding the words mashiv haruach umorid hagashem, "who makes the wind blow and the rain to fall", we begin saying instead morid hatal, "who causes the dew to fall".
Asking for rain, or dew, in England never seemed to make much sense. In Israel, however, dew is crucial for the growth of entire ecosystems. In parts of the Negev the average annual dewfall is greater than the average annual rainfall, and plants that grow there use every drop.
It is striking that while we ask for rain in prayer (during the Amidah) we do not ask for dew, we just mention it. The Talmud, teaches that the dew will come whether we ask for it or not. It is a constant sign of God's care and presence which we do not need to request. The Talmud has God say that Israel mistakenly wants Him to be like rain for them, dramatic, intermittent and obvious in His involvement, when really the deeper blessing would be for God to be to us like dew, a constant, quiet presence.