In Carnatic music Amruthavarshini is the raga that is supposed to get the rain. The raga Malhar is a powerful legendary in Hindustani classical music which is equivalent to Amruthavarshini. Even in Puranas, its written that in Thretayug, when Ravana set fire to Hanuman's tail, he set fire to entire Lanka. Then Ravana played the Amruthavarshini raga on his Veena and brought forth rain.
According to the legends, raga Malhar is so powerful that, when sung, it rains. The raga has lost its "swaroop" among the ages because there was no one who could remember its complicated rhythms and beats. Many great artists of Medieval period and much earlier period used to sing this raga.
There are lots of miracles that have taken place and are still taking place by singing and chanting krithis of Sri Muthuswamy Dikshitar. He attained mastery over the Veena, and the influence of Veena playing is evident in his compositions.
Sri Muthuswamy Dikshitar got the wonderful flow of music by the grace of Lord "Kumaraswamy" who put "Kalakanda" in his mouth. Soon he began to sing in praise of the Lord in a unique style by singing a kriti "Anandamritha Varshini" in raga Amruthavarshini", he caused the thunderous clouds to gather over the sky and rain profusely when there were no rains in that region for one year and the people yearned for water.
Once he was passing through the village Ettayapuram in thirunelveli District, there was an acute drought. Since he was well known for his powers, people in the village requested him to get rains in. At their request he sang the same kriti in Amruthavarshini raga. When he sang the line "varshaya varshaya varshaya" it started raining heavily flooding the village and he had to sing the same song with the slight modification. Instead of "varshaya varshaya varshaya", he used "sthambaya sthambaya" to stop the rains.
There are many written accounts of the raga. Meera Bai, the devotee of Lord Krishna is among noble singers those who were capable of having down the rains by various kinds of raga Malhar. She has composed between 200 to 1300 prayerful songs (bhajans), and most passionately praised Lord Krishna.
It is also true that certain ragas cause certain reactions, such as Deepak raga. Infact someone went to the extent of saying that singing this raga could cause a burning sensation and that is why there are no songs that are taught in this raga.
However, raga Amruthavarshini or raga Malhar better not sing in the monsoon season as the rain is already causing damages across the world.