Complex sentence: Summer has a lower local differentiation compared to winter, and since the inland areas are hotter than the Gyeonggi Bay area, the hottest area is Pyeongtaek, making the average temperature of August.
Split into simpler sentences: Summer has a lower local differentiation compared to winter. The inland areas are hotter than the Gyeonggi Bay area, the hottest area is Pyeongtaek, making the average temperature of August.