In plain words
The poet, of Kaṇṭam: When he saw the water-laden clouds arrive over [Āyppāṭi], thunder and pour down in torrents, he sheltered it beneath a mountain held up as a great umbrella: the home of Puruṣōttama, who loves Mathurā, is the eminent city called Kaṇṭam, on the bank of the Gaṅgā, where sages of hard penance plunge into its beating waves for the bath that closes a sacrifice, and the river sweeps away the ploughs and other implements of the sacrificial ground.