Tonight, in Eretz Yisrael, we begin saying ותן טל ומטר in שמונה עשרה. We started משיב הרוח on שמיני עצרת that is said in the blessings of שבח, or praises of Hashem. The ותן טל ומטר is in the category of בקשות, requests of Hashem. Therefore, tonight we begin asking for rain, as Jews have had two weeks to get home from their pilgrimage to Jerusalem on Succot.
If one forgets ותן טל ומטר, it depends when he remembers. One option is to insert it in the שמע קולינו blessing, when general requests are made. However, if one forgot after finishing שמונה עשרה, he must start the שמונה עשרה all over again.
We need to pray with great sincerity as it has been several years since we have had a rainy winter. The Kinneret is depleted and rain is a direct sign of Hashem’s abundant blessings.
May we be granted to be זוכה to receive Hashem’s blessings.