根据短文内容，判断下列各句正误。

    Here's the weather report for today. It's going to be dry and windy for most of the day. Because of the wind, it's going to be cooler than usual. And the wind is going to be stronger in the evening.

    Now the report for the weekend. Our Saturday morning is going to be cloudy with little rain. And it's going to be cooler than today. In the afternoon the clouds will lift and the sun will come out. We shall have a warm evening.

    On Sunday the weather is going to change again. It's going to be fine and hot. But at noon a wind will come and it's going to be stronger in the afternoon. It's going to be a little cooler in the afternoon.

205年一些大城市雾霾天气仍然非常严重，形成雾霾天气的原因是空气中PM2.5含量的增加，PM2.5指的是（　　）