Why did it suddenly get cold?

Air invasion, wind direction change, air pressure change, etc.

1. Cold air intrusion: When cold air flows in from the north or northwest, it is brought by high latitudes or cold areas. Cold air will replace the original warm air, causing the temperature to plummet.

2. Change of wind direction: Change of wind direction will also lead to sudden cold weather. Originally, the wind direction was warm wind blowing from the ocean, and suddenly it became cold wind blowing from the land, so the temperature would drop.

3. Air pressure change: The sudden drop of air pressure is the result of the change of weather system. For example, the proximity of a low-pressure system will lead to a drop in air pressure, which in turn will lead to a sudden drop in temperature.