Why is the lightning in Nanchang so loud?

Affected by subtropical high. Every June and July, the thunder and lightning in Nanchang will increase, which is normal. In summer, the atmospheric stratification at the edge of the subtropical high in the northwest Pacific is unstable, which is conducive to the occurrence of thunderstorm weather, and the thunder will be very loud, especially when the unstable energy is strong, the temperature and humidity distribution in the near-surface layer is uneven and the terrain conditions are favorable.