Let:

The speed of the sound decrases if the temperature is below 20. The change is 0.6m/s per ⁰C, so:

We can write the speed in terms of the distance and the time as follows:

So, for the light:

For the sound:

Since:

That's the reason why the smoke is seen before the sound is heard. The time delay for the sound of the pistol is 2.35 seconds