How accurate is the weather forecast for a region 15 days?

There is no exact value for this. As far as the current weather forecast is concerned, the accuracy of short-term weather forecast is very high, but it is only high, and it cannot reach the accuracy of 100%.

Weather refers to the specific state of the atmosphere near the surface in a short period of time.

Weather phenomenon refers to various natural phenomena in the atmosphere, that is, the comprehensive expression of the spatial distribution of various meteorological elements in the atmosphere (such as temperature, pressure, humidity, wind, clouds, fog, rain, flash, snow, frost, thunder, hail, haze, etc.). ) in an instant.

Weather process is the process of weather phenomena changing with time in a certain area.

All kinds of weather systems have certain time and space scales, and they are intertwined and influence each other.