Why is the weather in the Northeast so cold?

The latitude of the northeastern region of my country is north of 40° north latitude. In October, the direct point of the sun moves to the southern hemisphere, which is relatively far away from the northeastern region of the country. In Northeast my country, the height of the sun at noon is significantly reduced, the day is significantly shortened, and solar radiation is significantly weakened. In October, high pressures in Mongolia and Siberia begin to become strong, which are relatively close to the Northeast. Winter northerly winds affect the Northeast relatively early, so the cold season in the Northeast is relatively long. Some areas have now started to heat.