Q. If someone prayed maariv after plag but before the shkia on December 4, and forgot that you have to start saying that night veten tal umatar, but since it was not yet really night, does he have to repeat the amida?
A. Shulchan Aruch (O.H. 117: 5) rules that “shoalim” or the time we start the request for dew and rain at Maariv is on the sixtieth day after the “tekufa” or autumnal equinox began, which is typically the fifth or sixth of December in our days. We say it during maariv of the day before (fourth or fifth), because that is when in Halacha, December 5th. begins.
The day when the tekufa begins is counted in the sixty days. The equinox may begin at different times during the night or day. Biur Halacha (117) quotes Poskim that disagree if the sixty days are counted from the beginning of that day or from the hour it actually began. We usually begin the request at the beginning of the night on maariv. After the fact, when one forgot, Chaye Adam rules that we go after the hours time (me’es le’es) and it could be even in the morning. That changing time is expressed in Eretz Yisroel hours, and has to be adjusted to local time.
Therefore, Horav Shlomo Miller’s Shlit’a opinion is that although normally if one has already ended the amida and forgot to mention tal umatar, he has to repeat the amida even on an early maariv, on this first night, reflecting the doubt created by the above Poskim’s disagreement, one does not have to repeat the tefila. (Mekor Chaim and Kaf Hachaim and others rule similarly, since when in doubt we are lenient in blessings, Biur Halocho and others quoting a Chassam Sofer’s story, are stringent).
Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit’a