Where I live in summer I regularly get days with UV index above 15.
If you burn in 15 minutes under UV index 6 on the worst days that I've seen you'd burn in 5 minutes. So a SPF of 60 is as useful here like an SPF of 20 is wherever you live.
Jesus H Christ, UV index of 15? I thought the 12 we see in the middle of Texas summers was bad. I've burnt in 10 minutes through a windshield with that.
The UV index in the southern hemisphere goes a lot higher than anything you experience up in the northern hemisphere. Do yourself a favour and go have look at the UV index on a hot summers day in Sydney in January.
If you burn in 15 minutes under UV index 6 on the worst days that I've seen you'd burn in 5 minutes. So a SPF of 60 is as useful here like an SPF of 20 is wherever you live.