What's the weather like in Xiamen in mid-March? What should I wear?

Wear a thicker coat outside, and it is best to have long sleeves inside; Wear a long-sleeved T-shirt suit and knit cardigan. Don't wear long pants, or you will not stand it. By the way, you'd better take an umbrella that can be put in your bag, which is convenient. If there is no guide to show you around, prepare a map (or Google Maps on your mobile phone), which should be enough for you.