Why were people distressed by the rain?
The ninth month (December) was in the middle of the rainy season, and with the people standing in the rain in the temple courts, this was certainly not the best time for long discussions to take place. Possibly the people also saw the heavy rains as a sign of God’s displeasure (cf. 1 Samuel 12:17–18; Ezekiel 13:11, Ezekiel 13:13).1
9 Then all the men of Judah and Benjamin assembled at Jerusalem within the three days. It was the ninth month, on the twentieth day of the month. And all the people sat in the open square before the house of God, trembling because of this matter and because of the heavy rain.