Taanis, Chapter 1, Mishnah 7. Our Mishnah deals with a situation in which all the fasts listed in the previous Mishnayos have been completed, and the community still has not been answered with rain.
"Avru eilu v'lo na'anu":
If the last seven fasts have passed and they still have not been answered with rain, from this point on no further public fasts are added. Instead, a different approach is taken: cutting back on worldly affairs and on anything that involves joy.
"Mema'atin b'masa u'matan" - they cut back on business dealings, beyond what is absolutely necessary.
"B'binyan u'vinti'ah" - building that involves joy, and anything whose nature is joyous, as well as planting done for purposes of joy.
"B'eirusin u'v'nisu'in" - the betrothal of a man and a woman, and likewise marriage.
"U'vish'eilas shalom" - they cut back on greeting one another with a blessing of peace.
"K'vnei adam hanezufim laMakom" - like people who are under rebuke from Hashem, like those whom the Holy One, Blessed is He, has placed under a ban.
"HaYechidim chozrin u'misannin":
The distinguished individuals, meaning the Torah scholars, resume and continue fasting on Mondays and Thursdays, until the month of Nisan has ended.
"Yatza Nisan v'lo yardu geshamim - siman kelalah":
If the month of Nisan has passed and the rains still have not fallen, this is a sign of a curse.
And there are those who have the opposite version of the text: on the contrary, once Nisan has passed and rains do fall - that is the sign of a curse, since rainfall in this season points to something negative.
As it says: "Halo ketzir chittim hayom" - Shmuel said these words to the Jewish people in order to signal that the Holy One, Blessed is He, was not pleased with them. He said: today is the time of the wheat harvest, which is already after Nisan, and nevertheless he announced that there would be thunder and rain would fall, as a sign of something negative.
From here we learn that rainfall after Nisan is not a positive thing, but rather - Heaven forbid - is considered a negative sign.