How high is the temperature hot and how high is the temperature mild?

In middle school geography, under normal circumstances, the monthly average temperature higher than 15 degrees is called high temperature, 0- 15 degrees is mild, and below 0 degrees is cold. In most cases, except for a few cases. The most obvious is the temperate maritime climate. Although the average temperature in some months is higher than 15 degrees, it is characterized by mild and humid throughout the year. )