Why sometimes I only see lightning but can't hear thunder?

Usually in thunderstorm weather, lightning is always accompanied by thunder, but sometimes people only see lightning but can't hear thunder. How is this phenomenon caused?

Lightning is a spectacular and somewhat frightening discharge phenomenon accompanied by lightning and thunder. Lightning is usually produced in cumulonimbus clouds with strong convection, so it is often accompanied by strong gusts and heavy rains, and sometimes accompanied by hail and tornadoes. The top of cumulonimbus clouds is generally very high, up to 20 kilometers, and there are often ice crystals on the top of the clouds. The attachment of ice crystals, the breaking of water droplets and air convection make clouds generate charges.

The speed of sound propagation in air increases with the increase of air temperature, and the speed of sound propagation in warmer air is faster than that in colder air. If the temperature decreases upward, the upper part of the sound wave propagating in the horizontal direction propagates slower than the lower part, so the path of the sound wave bends upward.

Because the temperature near the ground is warmer and the temperature up is colder, the refraction of sound turns the sound up, so it can't spread far along the ground.

On the contrary, the sound waves of thunder are refracted upward by the warmer air near the ground, exceeding the range of 25 kilometers. Because the refraction of sound is so severe that it spreads upward, people on the ground can only see lightning and can't hear thunder.

The temperature of lightning varies from 17000 degrees Celsius to 28000 degrees Celsius, which is equivalent to 3~5 times the surface temperature of the sun. The extreme heat of lightning caused the air along the way to expand violently. Air moves very fast, so waves are formed and sounds are made.