We are suffering from water problem without rain. Any suggestions about rain generating Mantras are welcomed. This question may appear as a primarily-opinion based, but actually it is not. So, please don't close it.
The Rishis of vedic times stressed on treating nature and one’s environment with total reverence worthy of worship. So they created hymns in honor of every element of nature. Thus we can find prayers /Mantras for rain in different Hindu scriptures like Vedas and Upanishads.
अछा वद तवसं गीर्भिर आभि सतुहि पर्जन्यं नमसा विवास |
कनिक्रदद वर्षभो जीरदानू रेतो दधात्य ओषधीषु गर्भम || 5.83.1||
achā vada tavasaṃ ghīrbhir ābhi stuhi parjanyaṃ namasā vivāsa |
kanikradad vṛṣabho jīradānū reto dadhāty oṣadhīṣu gharbham ||
SING with these songs thy welcome to the Mighty, with adoration praise and call Parjanya. The Bull, loud roaring, swift to send his bounty, lays in the plants the seed. for germination.
दिवो नो वर्ष्टिम मरुतो ररीध्वम पर पिन्वत वर्ष्णो अश्वस्य धाराः |
अर्वाङ एतेन सतनयित्नुनेह्य अपो निषिञ्चन्न असुरः पिता नः || 5.83.6||
अभि करन्द सतनय गर्भम आ धा उदन्वता परि दीया रथेन |
दर्तिं सु कर्ष विषितं नयञ्चं समा भवन्तूद्वतो निपादाः || 5.83.7||
महान्तं कोशम उद अचा नि षिञ्च सयन्दन्तां कुल्या विषिताः पुरस्तात |
घर्तेन दयावाप्र्थिवी वय उन्धि सुप्रपाणम भवत्व अघ्न्याभ्यः || 5.83.8||
यत पर्जन्य कनिक्रदत सतनयन हंसि दुष्क्र्तः |
परतीदं विश्वम मोदते यत किं च पर्थिव्याम अधि || 5.83.9||
divo no vṛṣṭim maruto rarīdhvam pra pinvata vṛṣṇo aśvasya dhārāḥ |
arvāṅ etena stanayitnunehy apo niṣiñcann asuraḥ pitā naḥ ||
abhi kranda stanaya gharbham ā dhā udanvatā pari dīyā rathena |
dṛtiṃ su karṣa viṣitaṃ nyañcaṃ samā bhavantūdvato nipādāḥ ||
mahāntaṃ kośam ud acā ni ṣiñca syandantāṃ kulyā viṣitāḥ purastāt |
ghṛtena dyāvāpṛthivī vy undhi suprapāṇam bhavatv aghnyābhyaḥ ||
yat parjanya kanikradat stanayan haṃsi duṣkṛtaḥ |
pratīdaṃ viśvam modate yat kiṃ ca pṛthivyām adhi ||
6 : Send down for us the rain of heaven, ye Maruts, and let the Stallion's flood descend in torrents. Come hither with this thunder while thou pourest the waters down, our heavenly Lord and Father.
7 : Thunder and roar: the germ of life deposit. Fly round us on thy chariot water laden. Thine opened water-skin draw with thee downward, and let the hollows and the heights be level.
8: Lift up the mighty vessel, pour down water, and let the liberated streams rush forward.
9: When thou, with thunder and with roar, Parjanya, smitest sinners down, This universe exults thereat, yea, all that is upon the earth.
अद॑र्द॒रुत्स॒मसृ॑जॊ॒ वि खानि॒ त्वम॑र्ण॒वान्ब॑द्बधा॒नाँ अ॑रम्णाः ।
म॒हान्त॑मिन्द्र॒ पर्व॑तं॒ वि यद्वः सृ॒जॊ वि धारा॒ अव॑ दान॒वं ह॑न् ॥ 5.32.1 ||
adardarutsamasRujO vi khAni tvamarNavAnbadbadhAnA~M aramNAH |
mahAntamindra parvataM vi yadvaH sRujO vi dhArA ava dAnavaM han || 5.32.1 ||
Breaking open the cloud You create the channels (for rain)! You strike fast the mammoth cloud! Oh Indra! You cast open the mountain of cloud making the showers, destroying the darkness!
Here is an excerpt from the Chandogya Upanishad in which an insight is offered detailing a more scientific and logical approach to the importance of rain.
आपो वावान्नाद्भूयस्तस्माद्यदा सुवृष्टिर्न भवति व्याधीयन्ते प्राणा अन्नं कनीयो भविष्यतीत्यथ यदा
सुवृष्टिर्भवत्यानन्दिनः प्राणा भवन्त्यन्नं बहु भविष्यतीत्याप एवेमा मूर्ता येयं पृथिवी यदन्तरिक्षं
यद्द्यौर्यत्पर्वता यद्देवमनुष्यायत्पशवश्च वयासि च तृणवनस्पतयः श्वापदान्याकीटपतङ्गपिपीलकमाप
एवेमा मूर्ता अप उपास्स्वेति ॥ ७.१०.१॥
Apo vāvānnād bhūyasyaḥ | tasmād yadā suvṛṣṭir na bhavati vyādhīyante prāṇā annaṃ kanīyo `evemā |mūrtā yeyaṃ pṛthivī yad antarikṣaṃ yad dyaur yat parvatā yad devamanuṣyā yat paśavaś ca vayāṃsi ca tṛṇavanaspatayaḥ śvāpadāny ākīṭapataṅgapipīlakam | āpa evemā mūrtāḥ | apa upāssveti |
“Water is greater than food. Therefore, if there is not sufficient rain, living beings fail from fear that there will be less food. But if there is sufficient rain, they become happy because there will be much food. This water, by assuming different forms, becomes this earth, sky, heaven, mountains, gods and men, cattle, birds, herbs and trees, all beasts down to worms, midges, and ants. Water itself assumes all these forms. Meditate on water”.
The Veda mantras to bring rain are also to be found in the Atharva Veda (AV).
The Suktas, AV 4.15 and AV 7.18, are entirely dedicated to rain.
Samikshayantu tavishA prudAnvo (1) ApAm rasA oshadhimihi sachantAm (2) Varshasya sargo mahayantu bhumim (3) Prithag jAyantAm oshadhayo viswrupAh (4)
By the grace of mighty ones and auspicious donors (1), let the essence (rasa) in the waters come to the herbs (2). Let the gushes of rain gladden the earth (3); Let all forms of (medicinal) plants be born here and there.
In these Suktas, the Marut Gods, who are the helpers of Indra, are asked to propel the clouds to yield rain.
Some further mantras are as follows:
Apo viddhut abhram varpa sam vo avantu sudhAnava (1) UtsA ajagarA uta (2)
Let the waters, lightning, cloud, rain favour lavish givers (1), also favour the fountains and serpents (ajagarA).
Pra navasva prithivi bhindri idam divyam navah (1) Udro divyasya no dhAtarishAno vishvA datim (2)
Earth is asked to split the cloud of heaven. (1) and release the water in the bag.
Yet another mantra (only translation given) is:
Open and raise up (udacha) the great covering sheath and spribkle abundantly along with the lightning and wind. Let thew sacrifice be extended (tanvata) and released in amny ways. Let the growths of earth (oshadhayah) become full of delight.
Also, we should not doubt the fact that Yajnas (if properly done) can bring rains. As the scriptures clearly say that it can:
Manu Smriti 3.76. An oblation duly thrown into the fire, reaches the sun; from the sun comes rain, from rain food, therefrom the living creatures (derive their subsistence).
In Veda mantras, God Indra has been appealed to release rain in times of draught and to stop downpour in times of excessive rainfall.
Even, in these times, there have been persons who have displayed those powers at times of real need alone.
One such person was Sri Ganapati Muni (1878-1936), an adept in Vedas and Tantras and the first disciple of Sri Ramana Maharshi.
Now, those who want empirical evidences of experiments comprising of Yajnas bringing out rain in times when it is needed and stopping it when it has been excessive downpour, can read the book Vedic Metereology by Ravi PrakAsh Arya.
This book records over 400 such experiments, performed in various parts of India, over a period some 40 years in this century.
Several of these experiments have been successful and they have the following key features:
(1) Specification of the appropriate atmospheric conditions as relevant to each season; for instance, wind has to blow from a certain direction in a particular season.
(2) Performance of a prticular type of Yajna accompanied by chanting of Veda Mantras.
(3) Spiritual attainment of the person performing the Yjana. Absolute faith in the efficacy of the procedure is essential to its success. There can be no guarantee of the rain pouring down or its stopping, should an unbeleliever follow the procedure casually with meeting its prerequisites.
So, it is not as easy as chanting few mantras or performing few Yajnas and rain will start pouring down, but it is not impossible too.
Yes there are many mantras in the Vedas which are for rains. In fact yajnas are primarily performed for the well being of all the living creatures. Through the smoke of the yajnas the clouds are invoked and attracted to bring rain. Rain helps the flora and fauna thus creating the necessary balance in the ecosystem.
All living bodies subsist on food grains, which are produced from rain. Rains are produced by performance of yajna [sacrifice], and yajna is born of prescribed duties.
There are several instances when rain has came on the last day of grand yajnas like agnistoma.
Varuna yaagam is frequently held at the famous Tirumala Tirupati temple. It has brought good rains many times.
This year also Varuna yaga was conducted there.
Yajur Veda mentions that the waters with which Varuna is connected are the waters of the atmosphere. These waters are described as Apah, Maha-salilam the great waters which denote primeval matter from which the manifest world emerges. Aditi the great mother of all gods is also said to give birth to the manifest world. Aditi is thus equated with Apah. As Apah, Aditi is the creative energy which is active (YV.10.7).That is, Aditi the mother of all gods is Prakrti and Shakthi the manifesting or the creative power. The notion of her divinity rests upon her power as a woman, a womb or a mother to give birth to and to bring forth life and existence.
Varuna (son of Aditi) who resides among these waters (Apah) is therefore called the child of the waters (Apam shishu) in the best of mothers. It is explained; the expression ‘best of mothers’ refers to the protective and nourishing nature of the waters as mothers. They are the gracious guides and protective mothers; and, Varuna is their child.
[It is also said; since Varuna dwells in waters he was also called Apam Napat (Apam = water; Napat = fire), ‘Son of the Waters’ (RV.1.2.35). Apam Napat is also referred to as the embryo (garbha) of the waters (RV.7.9.3). It is said; the sun when he sinks into waters – to quench his thirst – becomes Varuna the fire in the waters (Apam Napat).
In the Yajna
Yajur Veda is the book of Yajnas. During an Yajna, Varuna along with Mitra is invoked and invited to take seat on the North side of the altar Yajna-vedi and requested to protect Rta the law of nature ; and also to bring good rains (YV. 2.3; 2.16). The invitation to Varuna to occupy the seat on the North is interesting. North is the direction of the gods; it is the direction of Soma initially (as per Brih. Upanishad) and then of Kubera the sub-divine who is friendly with gods. Thus, in Yajur Veda, Varuna was still the major god of the Yajna. In the later texts Varuna was, however, assigned a seat on the West where the sun sinks into sea and into the night.
The hymns in Atharva Veda in praise of Varuna ‘the most impressive deity among all the Vedic gods’ are lofty, more devout and ethical in tone. They pray for purity, forgiveness, and release from sins, and for moral strength against sinning further. The hymns rise to a pitch of exaltation as they sing the splendour of Varuna. In these hymns Varuna, more than any other Vedic god, appears as a mighty and merciful.
Of the many soulful hymns submitted to Varuna, the sixteenth hymn in the fourth book of the Atharva Veda sung by sage Vashista celebrating Varuna’s power and omniscience is often quoted and hailed by scholars as being among the most devote and forceful hymns in the Vedic literature
While mentioning his connection with waters Varuna is referred to as– Apam-adhipathi the Lord who resides in the primeval waters. These waters are described as of golden hue, pure and purifying; and, they are the material cause for creation (AV.1.33.1-3)
The Brahmanas, especially the Shatapatha Brahmana (SB) carry elaborate discussions about the relationship that exists between truth (Sathya) and waters. It said; truth is the same as waters for waters are the truth. Hence: ’whereby waters flow that is the form of truth. It is the waters indeed that were first made in the universe. When waters flow everything whatever that exists is produced.”(SB.10.5.4.1). Waters also symbolize the law. Water causes everything to exist and to grow in order. The waters are the reality (SB.220.127.116.11) and represent immortality (Amrtatavam va Apah – SB.18.104.22.168). They are the faith (Shraddaha) in life (Tai.Br.22.214.171.124). All gods and all beings are water; as they are the foundation and the ultimate source of the universe; and everything is contained in them (SB 10.5.4.4.15).
Varuna in Aranyakas
Varuna is briefly discussed in the Aitareya Aranyaka at two places; and both refer to Varuna’s mystical association with waters. There are no allusions to his Vedic glory as the sky-god, or as the king or as the governor of the laws.
The waters referred to in these passages are philosophical suggestions as they denote the primeval waters or the primeval matter. Here, the creation of waters and of Varuna comes about as an expression of the Supreme Being’s will or desire. It is metaphorically said that they were born out of the manas the mind of the Supreme Being. Varuna is the mythical symbol of primeval matter. Thus, philosophically, waters and Varuna stand for Prakrti or the Becoming. It is the first stage of manifest world.
Rishya Srunga Sloka
This was recommended by Shankaracharya of Kanchi to bring rainfall.
Sloka in English
Rishyasringaaya munaye vibhandaka sutaayaca
Namah saantadhipataye satyah sadvrishti hetave
Vibhandaka sutah sreemaan saantaadhipathir akalmashaha
Rishyasringa itignyaataha mahaa varsham prayachathu