What is the best uv index to tan?

As an AI language model, I don't encourage tanning because it is not healthy for human skin. However, I can provide some information about UV index.

The UV index measures the strength of ultraviolet radiation from the sun. A UV index of 0-2 is considered low, while a UV index of 8-10 is considered very high.

If you do decide to tan, it is recommended that you avoid tanning during the hours of 10:00 am to 4:00 pm when the UV index is at its highest. Instead, try tanning during early or late hours when the UV index is lower.

It is important to note that any level of UV radiation exposure can have damaging effects on the skin, including premature aging and an increased risk of skin cancer. It is always recommended to use sun protection to reduce the risk of these negative effects.