Why is Herzegovina generally hotter and drier than Bosnia?

Herzegovina is generally hotter and drier than Bosnia because of its geographic location and proximity to the Mediterranean Sea. While the Dinaric Alps largely block Mediterranean climatic influences from reaching the Bosnia region, Herzegovina shares a greater climatic affinity with the neighboring Croatian region of Dalmatia.1

This southern region is characterized by the Karst, an area of arid limestone plateaus that descend toward the coast. Consequently, areas like Mostar experience higher average temperatures and a distinct dry season from June to September, contrasting with the milder, more temperate conditions found in the northern and central parts of the country.21