Why does the daily weather forecast always turn into rain instead of sunny day, and sunny day is not sunny day?

Weather forecast is based on meteorological principles and meteorological data. The change of weather is influenced by many factors, including air pressure, humidity, wind direction and wind speed. Weather forecast is a complicated task, and even using the most advanced science and technology and models, it is impossible to be 100% accurate.

First of all, the humidity in the atmosphere is an important factor. When the humidity is high, water vapor will condense into clouds and eventually form precipitation, such as rain, snow or hail. Therefore, when the weather conditions are favorable for the formation of clouds, the forecast result is more likely to be rainfall.

Secondly, the climate system on earth is a complex interactive network. Changes in temperature and pressure in the atmosphere will lead to the formation and movement of wind. The direction and speed of wind will affect the movement and collision of air masses, thus affecting the distribution of precipitation. This means that a small mistake in the weather forecast may lead to completely different weather conditions.

In addition, the weather system has certain uncertainty. Even under given atmospheric conditions, small changes may lead to differences in weather forecasts. This is because there are many complex interactions and nonlinear effects in the atmosphere, which are difficult to accurately simulate and predict.

In a word, the accuracy of weather forecast is influenced by many factors, including atmospheric humidity, wind direction and wind speed. There may be some errors and uncertainties in the prediction results. Therefore, even if the technology of weather forecasting is more and more advanced, it is still impossible to guarantee accurate weather forecasting every day.