Why is the time for the college entrance examination fixed every year?

The decision to arrange the college entrance examination in July has been controversial in all walks of life for many years. Its main opinion is that the hot weather in July is very unfavorable to candidates' exams, teachers' marking and parents' care for candidates. Moreover, floods and typhoons frequently occurred in many provinces in southern China in July, which brought a lot of inconvenience to the organization of the college entrance examination, so the date was changed.