What does the O symbol in the weather forecast mean?

There are no clouds in the sky. Adding a zero after the weather number means that it will be sunny in this city tomorrow, and the symbol O means that there is no cloud in Wan Li, which means that the temperature is good and can reach above zero. Weather forecast (measurement) or meteorological forecast (measurement) is to use modern science and technology to predict the state of the earth's atmosphere in a certain place in the future.