What do you mean by bad weather?

Does the subject want to ask "what does heavy weather pollution mean?" The value of PM2.5 in the air is 200-300. According to certain standards, the air quality of PM2.5 is divided into six grades: excellent 0~50, good 50~ 100, light pollution 100~ 150, moderate pollution 150, heavy pollution 200~300 and serious pollution 300. PM2.5 refers to particles with a diameter less than or equal to 2.5 microns in the atmosphere, also known as particles that can enter the lungs. Rich in a large number of harmful substances, it stays in the atmosphere for a long time and has a long transportation distance, which has a great impact on human health and atmospheric environmental quality.