What is a southerly day?

The south wind is also called returning to the south sky. Generally speaking, it happens in spring in the south and occasionally in the north. Usually occurs in April of Gregorian calendar or after rainy season. The north calls this kind of weather resurgence, which generally lasts for a short time.

There are four distinct seasons in the north, and indoor air is often heated in cold season, so indoor humidity is much higher than outdoor air. So in spring, after the outdoor temperature rises, the indoor temperature is still higher than the outdoor air temperature, so it is difficult to have a southerly day, because water vapor is more likely to condense outdoors at a lower temperature.

In the south, it's different. After going south because of strong cold air or rainy winter, the indoor temperature often drops to a lower level.

The main hazard of southerly days is that the rapidly increasing steam changes phase when it meets a cold object, and quickly condenses and adheres to the cold object. The greater the temperature difference, the faster the adhesion speed.

In this way, once there is too much water vapor in the air, a large number of water droplets will easily condense on cold objects. Water droplets breed algae and mold, causing mildew in a large area; Water droplets lead to the decrease of insulation value, resulting in short circuit or poor contact;