"I will send you rain in its season, and the ground will yield its crops and the trees of the field their fruit." -- Leviticus 26:4

"...then I will send rain on your land in its season, both autumn and spring rains, so that you may gather in your grain, new wine and oil." -- Deuteronomy 11:14

" ... Then the LORD's anger will burn against you, and he will shut the heavens so that it will not rain and the ground will yield no produce, and you will soon perish from the good land the LORD is giving you." -- Deuteronomy 11:17

Easton's Bible Dictionary:

There are three Hebrew words used to denote the rains of different seasons,

(1.) Yoreh (Hosea 6:3), or moreh (Joel 2:23), denoting the former or the early rain.

(2.) Melqosh, the "latter rain" (Proverbs 16:15).

(3.) Geshem, the winter rain, "the rains." The heavy winter rain is mentioned in Genesis 7:12; Ezra 10:9; Cant. 2:11. The "early" or "former" rains commence in autumn in the latter part of October or beginning of November (Deuteronomy 11:14; Joel 2:23; Comp. Jeremiah 3:3), and continue to fall heavily for two months. Then the heavy "winter rains" fall from the middle of December to March. There is no prolonged fair weather in Palestine between October and March. The "latter" or spring rains fall in March and April, and serve to swell the grain then coming to maturity (Deuteronomy 11:14; Hosea 6:3). After this there is ordinarily no rain, the sky being bright and cloudless till October or November.

Rain is referred to symbolically in Deuteronomy 32:2; Psalm 72:6; Isaiah 44:3, 4; Hosea 10:12.

Noah Webster's Dictionary:

1. (n. & v.) Reign.

2. (n.) Water falling in drops from the clouds; the descent of water from the clouds in drops.

3. (n.) To fall in drops from the clouds, as water; -- used mostly with it for a nominative; as, it rains.

4. (n.) To fall or drop like water from the clouds; as, tears rained from their eyes.

5. (v. t.) To pour or shower down from above, like rain from the clouds.

6. (v. t.) To bestow in a profuse or abundant manner; as, to rain favors upon a person.

Int. Standard Bible Encyclopedia :

RAIN

ran (maTar, Arabic (?), maTar, "rain" geshem, "heavy rain" moreh, "early rain," yoreh, "former rain," malqosh, "latter rain"; brecho, huetos):

1. Water-Supply in Egypt and Israel:
In Egypt there is little or no rainfall, the water for vegetation being supplied in great abundance by the river Nile; but in Syria and Israel there are no large rivers, and the people have to depend entirely on the fall of rain for water for themselves, their animals and their fields. The children of Israel when in Egypt were promised by Yahweh a land which "drinketh water of the rain of heaven" (Deuteronomy 11:11). Springs and fountains are found in most of the valleys, but the flow of the springs depends directly on the fall of rain or snow in the mountains.

2. Importance of Rain in Season:
The cultivation of the land in Israel is practically dry farming in most of the districts, but even then some water is necessary, so that there may be moisture in the soil. In the summer months there is no rain, so that the rains of the spring and fall seasons are absolutely essential for starting and maturing the crops. The lack of this rain in the proper time has often been the cause of complete failure of the harvest. A small difference in the amount of these seasonal rains makes a large difference in the possibility of growing various crops without irrigation. Ellsworth Huntington has insisted on this point with great care in his very important work, Israel and Its Transformation. The promise of prosperity is given in the assurance of "rain in due season" (Leviticus 26:4 the King James Version). The withholding of rain according to the prophecy of Elijah (1 Kings 17:1) caused the mountain streams to dry up (1 Kings 17:7), and certain famine ensued. A glimpse of the terrible suffering for lack of water at that time is given us. The people were uncertain of another meal (1 Kings 17:12), and the animals were perishing (1 Kings 18:5).

3. Amount of Rainfall:
Israel and Syria are on the borderland between the sea and the desert, and besides are so mountainous, that they not only have a great range of rainfall in different years, but a great variation in different parts of the country.

The amount of rain on the western slopes is comparable with that in England and America, varying from 25 to 40 inches per annum, but it falls mostly in the four winter months, when the downpour is often very heavy, giving oftentimes from 12 to 16 inches in a month. On the eastern slopes it is much less, varying from 8 to 20 inches per annum. The highest amount falls in the mountains of Lebanon where it averages about 50 inches. In Beirut the yearly average is 35, 87 inches. As we go South from Syria, the amount decreases (Haifa 27, 75, Jaffa 22, 39, Gaze 17, 61), while in the Sinaitic Peninsula there is little or none. Going from West to East the change is much more sudden, owing to the mountains which stop the clouds. In Damascus the average is less than 10 inches. In Jerusalem the average for 50 years is 26, 16 in., and the range is from 13, 19 in 1870 to 41, 62 in 1897. The yearly records as given by J. Glaisher and A. Datzi in Palestine Exploration Fund Quarterly from 1861 to 1910, 50 years, are given in the accompanying table.

The following Prayer for Rain consists of two prayer-poems, composed by the famous paytan, Rabbi Elazar ha Kallir, who lived about 1300 years ago.
The first of these begins with the word Af Bri, which is the name of the angel of rain:

Af Bri is the title of the prince of rain,
Who gathers the clouds and makes them drain,
Water to adorn with verdure each dale,
Be it not held back by debts left stale,
O' shield the faithful who pray for rain...

May He send rain from the heavenly towers,
To soften the earth with its crystal showers,
You have named water the symbol of Your might,
All that breathe life in its drops to delight,
O' revive those who praise Your powers of rain...

The second part of the Prayer for Rain consists of a poem beginning with the words zechor av, Remember our father Abraham. It is an alphabetical acrostic, each line beginning with a letter of the Hebrew alphabet (excluding the word "Remember" at the beginning of each stanza), and finishing with the word mayim -- Water. It refers to the good deeds of our ancestors Abraham, Isaac, Jacob, Moses and Aaron, and lastly the twelve tribes, and the miracles that were shown to them in connection with water. In their merits, and for their sakes, the Jewish people pray to G-d for rain:

Our G-d and G-d of our fathers,
Remember our father Abraham who was drawn after You like water,
Whom You did bless like a tree planted near streams of water,
You did shield him, You did save him from fire and water,
You did try him when he sowed by all streams of water,
For his sake, do not refuse water.

Remember Isaac whose birth was foretold over a little water,
You did tell his father to offer his blood like water,
He too was heedful in pouring out his heart like water,
Digging in the ground he discovered wells of water.
For his righteousness' sake, grant abundant water.

Remember Jacob who, staff in band, crossed the Jordan's water,
His heart attuned to You, be rolled the stone off the well of water,
When he wrestled with the angel of fire and water,
You did promise to be with him through fire and water.
For his sake, do not refuse water.

Remember Moses in an ark of reeds drawn out of the water,
They said: He drew water and provided the flock with water,
And when Thy chosen people thirsted for water,
He struck the rock and there gushed out water,
For his righteousness' sake, grant abundant water.

Remember the High Priest who bathed five times in water,
He bent and washed his bands with sanctified water,
He read from the Scriptures and sprinkled Purifying water,
He kept a distance from a people turbulent as water,
For his sake, do not refuse water.

Remember the twelve tribes You did bring across the water,
You did sweeten for them the bitterness of water,
For Your sake their descendants spilt their blood like water
Turn to us, for our life is encircled by foes like water.
For their righteousness' sake, grant abundant water.

For You are G-d, who causes the wind to blow and the rain to fall.
For a blessing, and not for a curse -Amen!
For life, and not for death -Amen!
For plenty, and not for scarcity --Amen!