Let it Rain

This past מוצאי שבת we began reciting ותן טל ומטר לברכה.  Here is the relevant passage from the Ezras Torah calendar:

MOTZIE SHABBOS, DEC. 4, 28 KISLEV 

At Maariv, we begin to include "ותן טל ומטר לברכה" into the Shemonah Esrei. If one became aware, after he had completed the Bracha מברךהשנים , that he had omitted "ותן טל ומטר לברכה" he should wait to insert it right before כי אתה שומע of  Shma koleinu.    If he had already completed the Bracha  Shomea Tefila, he may insert it before saying "רצה". If he had already begun "רצה" he must return to the Bracha " ברך עלינו", which is the proper place for ותן טל ומטר לברכה. If he had already completed the Shemonah Esrei and stepped backward, then he must repeat the entire Shemonah Esrei. In any situation in which a person must repeat the entire Shemonah Esrei, he may fulfill his obligation by listening to every word of the Chazzan's Repetition from begining to end, with the intention of thus fulfilling his obligation. (It is advisable to repeat 101 times [at the very least 90 times]: " טל ותן לטובה תבואתה מיני כל ואת לברכה ומטר" so as to make the inclusion of "ותן טל ומטר לברכה" habitual and fluent, thus eliminating any future doubt as to whether one included "ותן טל ומטר לברכה" in the Shemonah Esrei or not.) 

For an extensive summary of why we (those outside of Israel) are dependent on the secular calendar, see here.