We are planning to go Shantou on the coming month of October, may I know what is the temperature?

It is nice to travel to Shantou in October with a mild and pleasant weather. The average temperature is about 21~28C. You can take some light clothes like T-shirts and shorts plus a jacket in case.
Travelling to that place, you should not miss Nan Ao Island, Qing Ao Bay and Citic Resort, Lotus Peak, Queshi Scenic Spot and Symbolic Tower of the Tropic of Cancer.
Chao cuisine, a branch of Cantonese cuisine, is very popular local cuisine. You could hace a taste of the famous dishes, such as Shang Tang Ju Bao (Steamed Abalone in Condensed Soup), Suancai Baishan (Boiled White Eel Packaged in Pickled Vegetables), and Jingua Yuni (Pumpkin with Mashed Taros inside). 3-4 days are OK for you to have a trip there. You'd better find a hotel at the city centre area.