毎年12月に気温が下がります。
The temperature goes down in December every year.
The temperature gets lower in December ever year.
The temperature becomes cooler in December every year.(①）
The temperature becomes colder in December every year.（②）
The temperature becomes lower in December every year.
毎年7月に気温が上がります。
The temperature goes up in July every year.
The temperature rises in July every year.
The temperature gets higher in July every year.
The temperature becomes warmer in July every year.(①）
The temperature becomes hotter in July every year.（②）
①と②がそれぞれ反対の言い方になります。