Can I swim in Rizhao on July 5th?

It depends on your own physical condition. Judging from previous years, the water was still quite cool in the evening at that time. If the weather is good, you can choose to go into the water at noon, but it will be very sunny, so you need to use waterproof sunscreen. The best time to swim at Rizhao Beach is when the maximum temperature is around 33 degrees, which is probably around the end of July or early August.