All week long, it seems you sit inside at school when it is fine outside. But when the weekend comes, it is very cloudy. There is rain according to(根据) the weather report.
Scientists studied more than 40 years of weather data(数据) from around the world. It shows weekend weather is different from weekday weather in some places.
Part of the study involved(包括) 660 weather stations in the US. At more than 230 of these places, the weather on Saturday, Sunday and Monday was different from the weather on Wednesday, Thursday and Friday. The difference was small, but the pattern was striking enough to make the scientists take notice.
"This kind of weekly rise and fall doesn't line up with any natural cycles, "the scientists say. Instead, they think that air pollution from human activities makes the weather become different.
