Is it appropriate to wear 3 to 5 cm thick-soled sandals when going out in summer?

This depends on personal preference and comfort. Here are some suggestions:

1. Comfort: Thick-soled sandals may provide additional support and cushioning for long periods of walking or standing. Probably more comfortable. However, if you are not used to wearing high heels or platform shoes, you may feel uncomfortable or unstable.

2. Type of activity: If you plan to engage in more active outdoor activities, such as hiking, hiking or visiting scenic spots, a thicker bottom may provide better stability and protection. But if you plan on doing more relaxed activities, like shopping or walking around the city, a thicker bottom may not be necessary.

3. Terrain and Weather: If you plan to be active on uneven or rugged terrain, a thicker bottom can provide better grip and protection. Also, if the weather is hot, a thicker base may cause your feet to sweat excessively or be non-breathable.