The weather forecast said that the air humidity was 68%, but after I opened the window for ventilation, the indoor humidity dropped to 19%. What is the reason?

The weather forecast measures the highest air humidity, which is not consistent with the humidity situation at home.

Plus: In humid weather, the way of opening windows should be: close the doors and windows facing south or southeast, that is, in the windward direction, only open the doors and windows in the downwind direction to reduce water vapor from entering the room. The air from the south wind is the wettest, and the furniture will be moldy if it is not done.

When the weather turns fine, all doors and windows can be opened to accelerate the evaporation of water. However, the outdoor air humidity is at the highest value at noon, so it is not suitable to open the window. It should be adjusted in the afternoon or at night when the climate is dry.

In addition, when opening the north window, we should also pay attention to the distance between the window and the north building. If the distance is too close, it will reflect the air from the south. Therefore, it is necessary to appropriately reduce the window opening time.