Affected by external sand dust transmission, Beijing's PM10 can reach severe and above pollution levels.

According to the Beijing Environmental Monitoring Department, it is predicted that from the afternoon to evening of the 21st, Beijing will be affected by the rear of a low-pressure system and the front of a high-pressure system, resulting in strengthened northwest winds. Foreign dust will gradually affect most parts of Beijing, with the PM10 concentration levels expected to significantly increase in the afternoon and evening, reaching peak concentrations of over 500 micrograms per cubic meter, indicating severe pollution levels. Due to strong winds, it is expected that the dust belt will gradually move out of Beijing in the early morning of the 22nd, with air quality improving to level 1-2 good on the 22nd daytime.