HOW TO INVOKE THE RAIN GOD?

As per Vedic tradition, there is a Yajña known as the KArIri Ishti for invoking the Rain God.

In addition we have:
1. VaruNa Mantra
2. RishyaSringa Slokas
3. Azhi Mazhai KaNNa ( of TiruppAvai)

These are very powerful in invoking the rains.
In Music , it is Amrutavarshini RAga.