Note: Commonly used metals are collectively referred to as gold, silver, copper, iron and tin, but only four kinds are mentioned in the title, so Wuxi is at the bottom.
Warm season: Kunming.
Explanation: Kunming is a special city in China. It is spring all the year round. This mystery is often faced with four seasons like spring, so Changchun is not at the bottom, because it is spring.