When a sound is reflected from a distant object, an echo is produced. Let the distance between the reflecting surface and the source of sound production remains the same. Do you hear an echo sound on a hotter day?

Given:

It is observed that when a sound is reflected from a distant object, an echo is produced.

To do:

To determine whether an echo sound is heard on a hotter day if the distance between the reflecting surface and the source of sound production remains the same.

Solution:

Let us know first what is an echo.

Echo formed by sound waves: 

When the repetition of sound is occurred due to the reflection of sound from the surface (e.g. wall, ceiling), it is called echo.

When echo is formed by a sound wave:

An echo is formed when the sound is reflected from the walls and ceiling in a vacant room.

When an echo is heard:

An echo is heard when the time interval between the reflected sound and the original sound is at least $0.1\ seconds$. As the temperature increases, the speed of sound in a medium also increases.

Echo on a hotter day:

On a hotter day, the time interval between the reflected and original sound will decrease and an echo is audible only if the time interval between the reflected sound and the original sound is greater than $0.1\ s$.  An echo is heard sooner on a hot day because the speed of sound in the air increases with temperature. So the speed of sound in the air is more on a hot day, and an echo is heard sooner.