Why does sound travel faster on a rainy day than on a dry day?

Explanation

The amount of water vapours present in the atmosphere is much higher on a rainy day than on a dry day. As the water vapours are lighter than dry air, density of wet air becomes less than of dry air. Because the speed of sound is inversely proportional to the square root of the density, sound travels faster on a, rainy day than on a dry day.