Why is there fog at 25 degrees Celsius in summer? Is it normal weather?

Normal, as long as the appropriate weather situation and water vapor conditions are met, it is possible to fog. However, due to the low temperature in winter, it is easier to reach or approach the dew point temperature. If there is a stable weather situation, such as L-shaped high pressure, it is easy to fog. In summer, the temperature is generally high, and the temperature difference with the dew point is large, so it is not easy to produce a stable weather situation conducive to summer fog, so there is little foggy weather in summer, but it is not absolutely absent.