The Weather I haven't seen the blue sky for a long time in Beijing, beacuse of the smog or haze(I am not sure which one is the best word to describe the weather, so I write both of them.), most of people who live in Beijing have to wear mask before they leave home. Yes , what I will talk about today is PM2.5(particulate matter). The smog is very harmful, not only for body , but also for the traffic. The smog will lead to / cause the cough， and the tiny PM once goes into your body when you breath, it hardly ever leave . it is harmful for good. Let's assume a situation, you drive on freeway and come across such the smog day ,what will happed ? The answer is traffic accidents. Beacuse you can't see the way clearly and your car is high speed. I cherish such a good weather, and the blue sky makes me happy ,and you ?