What do you mean by severe weather?

does the subject want to ask "what do you mean by severe weather pollution"? The PM2.5 value in the air is 2-3. According to certain standards, the air quality of PM2.5 can be divided into six grades, excellent ~5, good 5~1, light pollution 1~15, moderate pollution 15~2, heavy pollution 2~3 and serious pollution above 3. PM2.5 refers to particulate matter with a diameter less than or equal to 2.5 microns in the atmosphere, also known as particulate matter that can enter the lungs. It is rich in a large number of harmful substances and has a long stay in the atmosphere and a long transportation distance, which has a greater impact on human health and atmospheric environmental quality.