Why is the climate in northeastern Honshu, Japan?

The location of Honshu Island is as follows:

More details:

Most of them are temperate maritime monsoon climate, rainy in early summer and typhoons in autumn. Most areas are mild and humid, but there are obvious differences between north and south and east and west. The annual average temperature in Aomori in the north is 9.6℃, while Shimonoseki 15.5℃ in the southwest, with a difference of nearly 6℃. The average temperature in Leng Yue (65438+1October) is about -2℃ in the north and 5.5℃ in the southwest. The average temperature in the warmest month (August) is 22.5℃ in the north and 26.7℃ in the southwest. The annual precipitation is 1400 mm in the north and 1700 mm in the southwest. The eastern Pacific slope has the most precipitation in summer and typhoon period, less snowfall in winter and sunny weather; However, the western slope of the Sea of Japan is cloudy and snowy in winter, forming the Zita Law Belt. What is the forest area? 3/5。 The East Pacific coast has more precipitation in summer and autumn, less snowfall in winter, sunny weather, and the coast of the Sea of Japan is cloudy and snowy in winter. The river network is dense and the river is short. The larger rivers are Xinnong River and Yinchuan River, and there are many rapids and waterfalls in the middle and upper reaches of each river, which are rich in hydraulic resources.