At Maariv tonight, 7 Cheshvan, in Eretz Yisroel, we begin to say Vesein Tal Umatar during the Shemonah Esrei in the bracha of Boreich Aleinu. Residents of chutz laaretz won’t start saying it until December.
The 7 Cheshvan date is based on the shitah of Rabban Gamliel, who says that tefillah for rain is suspended until fifteen days after Sukkos, so that the last of the olei regel returning home to Bavel from Yerushalayim will reach the River Euphrates and not be delayed by the rain.
In chutz laaretz, we wait until December 4th based on the shitah of Chananiah to wait until 60 days after the Yomim Noraim.
If one became aware after completing the bracha of Mevareich Hashanimthat one omitted Vesein Tal Umatar, one should wait to insert it right before “Ki atah shomeiah” in Shema Koleinu.
(It is advisable to repeat 101 times [and at the very least 90 times] “Ve’es kol minei sevu’asah letovah vesein tal umatar” so as to make the inclusion of Vesein Tal Umatar habitual and fluent, thus eliminating any future doubt as to whether one included Vesein Tal Umatar in Shemonah Esrei or not.
Please feel free to print this out and hang it up or distribute it in shuls and yeshivos.
{Matzav.com Israel News Bureau}