Why can weather calendars in various regions predict the weather very early?

A small part of the weather can be predicted by visual inspection.

For example, the cloud system at the front of the cold front is used to predict the weather when the cold front passes, and the development of topographic clouds is predicted according to the front of topographic clouds, so is the cloud system on the sea surface.

They can be predicted by visual inspection, because they have their own changing rules, some of which can be seen by people.

But what can be predicted by visual inspection is only the tip of the iceberg. The purpose of modern weather forecast is to forecast all kinds of weather in the next few days or even a week 365 days a year. It is completely different from several weather records in history books.