Why is the weather forecast in Shenzhen always inaccurate?

Shenzhen is a coastal city, which is obviously affected by the sea breeze and the weather changes rapidly. In addition, the weather in Shenzhen in spring is mostly rainy, and the weather forecast can only predict the overall weather conditions for a few days or even a week or two, so we can only judge whether the weather is sunny, cloudy or rainy by the weather conditions of the day, so the weather forecast is really not very accurate.