What's the weather like in Harbin in mid-September?

I come from Harbin. Many people wear long sleeves now, and it will be colder in September. It is most appropriate to use a proverb to express the current weather: "Wear a cotton-padded jacket in the morning and yarn in the afternoon". Sooner or later, it will be colder. It's hot at noon, but short sleeves are ok. You can't wear skirts. Of course, you must get your pants ready. It will be very cold if it rains.