Orach Chaim 117:1 says that we begin Tal Umatar in Eretz Yisrael on 7 Cheshvan.
See also Aruch Hashulchan 117:2 where he mentions the reason for first beginning on 7 Cheshvan is to give the Olei Regalim time to get back home before the rains.
Chabad.org says
The Jews of ancient Israel made three pilgrimages to Jerusalem each year, for the holidays of Passover, Shavuot and Sukkot. Now, the official rainy season begins on Shemini Atzeret, when the Jews were about to start their journey back home after the festival of Sukkot. As much as they wanted the rain, they chose to delay their supplications in the interests of a safer and easier trip.
That is how the practice of delaying the prayer for rain began. In Israel, the prayer was begun only 15 days after Shemini Atzeret (the 7th of Cheshvan), allowing enough time for even the Jews living near the Euphrates to return home This custom is followed by Jews living in Israel until today.
Question:
As we are concerned about the rains, why don't we stop saying Tal Umatar from Rosh Chodesh Nissan to allow the Olei Regalim to arrive for Pesach without the rains? Why do we say Tal Umatar up to Pesach?