"Bring your thick clothes in the mountains" means that the person should pack and bring warm and thick clothing when traveling to a mountainous area. The climate in the mountains is usually colder than the surrounding lowlands, and temperatures can drop significantly, especially at higher altitudes. Therefore, it is essential to bring appropriate clothing to stay warm and protect yourself from the cold. Thick clothes such as jackets, sweaters, and long pants are recommended to keep the body warm and comfortable. It is also a good idea to bring hats, gloves, and other accessories to protect the extremities from the cold.