Why is the weather forecast never accurate?

Weather forecast is a kind of speculation, and the main means used are: satellite images, experience, observation and so on. Satellite cloud picture is the result obtained by calculating the trend and current distribution of satellite cloud picture observed by satellite with computer. This is a probability. As we usually say, the possibility of things happening is more or less the same, not necessarily like that. Satellite cloud images observe cloud water vapor, cold and warm airflow, etc. First of all, it is unpredictable, even if it is covered by clouds, it will not necessarily rain. Experience is accumulated by people for many years, but there will be subtle changes. For example, in Suining, Sichuan, rice harvesting usually started in mid-September, but it was delayed by 10 to 15 days in 2005. The weather is the same. There is also observation, that is, observation of biological changes and wind direction, temperature and so on. Many creatures have the ability to predict weather changes. There are many reasons for determining urban temperature, especially in recent years, the heat island effect is very serious, which makes the temperature more unpredictable, and the difference may be 3 to 5 degrees.