This conveys to us the responsibility that every single person has towards the global concern for beneficial rain.

We know that some people mistakenly begin Tal uMatar after T'filat Geshem, together with Mashiv HaRu'ach...

Rosh HaShana: Reference to G-d's remembering No'ach - lots of water, Tashlich - water.

Shabbat Shuva, Haazinu: Torah compared to dew, rain, downpour, shower.

Yom Kippur: Kohein Gadol washing his hands and feet ten times during the day, immersing in a mikve five times. Kohein Gadol's first prayer after coming out of Kodesh HaKodashim deals with rain.

Sukkot: Nisuch HaMayim in the Beit HaMikdash, Simchat Beit HaSho'eiva, the taking of four water-needy species, Hoshanot and Hoshana Rabba including the striking of the ground with the Aravot (River Willow) to will the ground to give forth its water. Rain on Sukkot is considered a sign of G-d's being upset with us.

Sh'mini Atzeret: T'filat Geshem.

Shabbat B'reishit: Creation and separation of the upper and lower waters (day two), gathering the waters to form oceans and land, emphasis on the mist over the land, then rain when Adam is created, the four rivers that flow from Gan Eiden.

Parshat No'ach: Need we go into detail? Rain, too much rain, flood, destructive waters.

Water - literally, and figuratively as Torah - is the most essential item in our lives.

Our Sages show us this importance of water by the rules they gave us for the Amida.

If one neglects to mention G-d as the Rainmaker or, at least, His involvement in the weather - omitting Mashiv HaRu'ach uMorid HaGeshem, which we are supposed to say, and not even saying Morid HaTal in its place - invalidates the Amida. Same for not saying Tal uMatar in its season.

Chazal could have said that these omissions do not invalidate 19 brachot of the Amida and require full repetition of the Amida - they say that for Zochreinu L'Chayim, Al HaNisim, Yaaleh v'Yavo at Maariv of Rosh Chodesh. But they didn't.

This conveys to us the responsibility that every single person has towards the global concern for beneficial rain. We are all in this together - we each must do our share.