What's the difference between the weather forecast 30-20 and 20-30?

The weather forecast "20-30" broadcast at night means that the lowest temperature is expected to be 20 and the highest temperature is 30 during the day from the broadcast night to the next day.

The weather forecast broadcast during the day is the antonym of "30-20", which means: it is expected that the maximum is 30 during the day and the minimum is 20 at night.

In addition, 20, 30 and other values are expected, not necessarily just 20 or 30.