In Israel, the month of Cheshvan is a month of transition. The summer and the chagim are over and we look to the winter for our annual rainfall. The fact that in Israel we must rely on the winter's rain to sustain us through the long dry season only stresses our dependency on Hashem. Rain symbolizes our special relationship with Hashem.
Unlike in His relationship with other nations, Hashem communicates with Am Yisrael showing His satisfaction for our actions in the amount of rain he gives us. We recite daily in the Shema "And it will come to pass that if you continually hearken to My commandments that I command you today, to love Hashem, your G-d, and to serve Him, with all your soul - then I will provide rain for your land in its proper time, the early and the late rains, that you may gather in your grain, your wine and your oil."
The opposite is true as well: we know that when there is a drought, it is a message for us to change our ways.
The name Cheshvan is not used in the Nevi’im; rather we find the name of this month recorded as Bul. The Radak (Melachim I 6:38) brings two explanations for this name. He first comments that this name comes from the root of mabul - flood, as the rains start in this month. The second explanation he brings links the word bul to the root of yevul, crops. This is confirmed by the Targum: "The month of gathering produce."
Interestingly, this root is also linked to the root for the word to wither (see Rashi). These two opposite meaning words together really symbolize the month - the withering of the old plants in the field and the planting of the new crops. This is the cycle of life as one season passes into another. The Midrash brings all these ideas together: "This month is the one in which the great Flood took place. It is the month in which the rains begin to fall again, thus is decreed. It is the time of destruction the like of which the world has never seen, and at the same time it is the time of rebirth, of withering and renewal."
On Sukkot, Chag HaAsif, we completed the agricultural cycle and harvested the crops, the product of the rain we received the previous winter. Right away we must begin to worry about the next year's rain. As it says in Masechet Rosh HaShana, on Sukkot we are judged for the coming year's rainfall. This is a constant reminder of how delicate our situation is. It serves to warn us not to become too haughty while harvesting our fruits, since the true source of all we have is Hashem.
On Shemini Atzeret we began to express our need for rain for the new year with Tefillat Geshem, the prayer for rain, in which G-d is acknowledged as the source of rain and the change of seasons, and which contains petitions for the crops and for preservation from famine. In Israel, we stopped saying morid hatal (Who makes the dew fall) and switched to saying mashiv haruach umorid hageshem (Who makes the wind blow and makes the rain fall). This switch is an important one.
In the Diaspora, most communities do not say morid hatal. This practice is based on the gemara in Ta’anit which says that it is not necessary to pray for tal since the dew, is something that Hashem always provides, no matter how we act. Tal represents that part of our relationship with G-d which will never be broken, no matter how much we sin.
In Sefer Melachim Alef, Eliyahu, in expression of his anger at the people for worshipping idols, decrees that there will be no rain or dew. Hashem cooperates with Eliyahu and brings a drought, stopping the rain for three long years. He allows Eliyahu to take away the people's rain to teach them a lesson, but he does not stop the dew.
It is like the relationship between a parent and a child. A parent may get angry with a child and punish the child. That would be like Hashem taking away our rain. But beneath that anger is the love that the parent feels for a child which is always there, no matter how angry he or she is about some specific thing the child has done. The tal is a constant, it is always there for us, and we can count on it always being there.
So why do we in Israel say a prayer for tal? Because it is important also to notice the steady things and not take them for granted, to appreciate the day to day things in life. If tal is Hashem's reminder to us that he always loves us, as it represents His chessed, the rain with its dual capacity for blessing and destruction represents the attribute of din, judgment. Rashi (Devarim 32:2) notes this difference and says that dew is something with which all rejoice, while rainfall brings dismay to some, for example, wayfarers, or someone with a cistern filled with wine.
While chessed is constant and gentle, din can be powerful and dangerous. Rain can be a blessing but also a curse, can fill the reservoirs or can flood, which is why the Tefillat Geshem ends with our beseeching Hashem to bring the rain "for blessing and not for curse, for life and not for death for plenty and not for scarcity."
With the saying of Tefillat Geshem, we start acknowledging G-d as the provider of rain, though we do not yet ask for the rain. Mashiv haruach u'morid hageshem is inserted in the beginning of the Amida into the blessing Gevurot, or Strength, in the section of Praise, as an expression of the power of Hashem, which includes being the source of life-giving rain. Gevurot is the blessing which ends with techiyat hameitim (revival of the dead), because rain, too, has the power to revive. The Gemara in Ta’anit 2a refers to this insertion as Gevurot Geshamim.
Praying for rain (she'elat geshamim) begins only on the 7th of Cheshvan in Israel (27th of November in the Diaspora). This appeal for rain is placed in the middle section of the amida, which is the part of the tefilla where requests are made. The delay in she'elat geshamim after Gevurot Geshamim is to allow the olim laregel to return home safely before requesting rain. In fact, we see the link between the merit of the olim laregel and an assurance of a good year of rain in Zecharia 14:17: "And it shall be, that whoso of the families of the earth goeth not up unto Jerusalem to worship the King, the L-rd of hosts, upon them there shall be no rain."
This chapter discusses the future when all nations will be oleh laregel on Sukkot, and those that choose not to come will be punished by not receiving rain that year. In Zecharia (8:9-12) the navi describes the world in the end of days. The navi describes a time not like ours, a time when "the ground shall give her increase, and the heavens shall give their dew". The dew, through Hashem's chessed, will be enough for the crops to grow, and we will be assured of an abundance of blessing that is not tied into the reward of man.
With the beginning of Cheshvan and the end of the chagim, we pray for the rain that reflects the world of reward and punishment. This task is a much greater one than the prayer for dew. It makes demands on us; it requires us to be involved. It is on our shoulders whether the rain will come. As we come out of the holidays of Tishrei we are at our strongest and are given a new start to try to be worthy of a rainy season. May this year bring answers to our prayer veten tal umatar levracha - may the dew and the rain fall as a blessing!