Why can northwestern Fujian be colder than coastal Fujian?

The coastal region of Fujian experiences a semitropical climate, whereas the northwestern part of the province is characterized by a temperate climate that can become cold in winter.1

This temperature difference is primarily due to the province's relief. While the coast consists of narrow plains, the interior is dominated by mountainous terrain, specifically the Wuyi Mountains, which reach elevations of approximately 6,000 feet (1,800 metres). These higher elevations in the northwest contribute to colder winter conditions, where precipitation occasionally falls as snow, unlike the milder winters found along the coast.21