Question

Velocity of sound increases on a cloudy day. Why?

Answer 1

The density of air reduces as humidity and amount of water in the air increases.  The speed of sound is inversely proportional to the root of density, therefore sound travels faster on a cloudy day than on a dry day so, velocity of sound increase.

Answer 2

Answer:

Because there's a decrease in density.

Explanation:

For fluids, the speed of sound (Vs) is given by the relationship :

$V_{s}=\sqrt{\frac{K_{s}}{d}}$, where:

Ks = coefficient of stiffness, the isentropic bulk modulus (or the modulus of bulk elasticity for gases).

d = density of the fluid.

As we can see, speed of sound is inversely proportional to density. If density decreases, speed of sound increases.

In a cloudy day, humidity is very high (in fact, when it rains, relative humidity is 100% (maximum) which is why the clouds can't hold any more water). Density is inversely proportional to humidity. So, in a cloudy (or highly humid) day, density decreases, causing an increment in the velocity of sound.