I often find flashes like thunder behind my mountain. Excuse me, what could it be?

According to the information you provided, you often find a flash like thunder, which may be lightning. Lightning is a strong discharge phenomenon between clouds and the ground, which usually occurs in areas covered by rain clouds. In addition, lightning may occur in sunny days, especially in isolated trees, towers, wilderness and other places. If you are worried that this flash may pose a threat to your safety, it is recommended that you contact the local weather forecasting agency or relevant departments in time to obtain more accurate information and safety suggestions.