Direct sun exposure when the UV index is under 3

That's before 9am or after 6pm around this week https://uv.willyweather.com.au/nsw/sydney/sydney.html

Yep and that's a UV index of 13 [Extreme] even whilst cloudy.

Australia and New Zealand have the highest melanoma rates in the world. We thus have a paranoia of "taking care not to burn", during office hours when UV is most intense.

The problem here is that UVB levels, required for vitamin D synthesis, decrease dramatically before 9am and after 6pm, whereas UVA does not. The best option for vitamin D synthesis is short sun exposure around midday.

Here are some interesting charts showing forecast and actual-measured UV index around NZ: https://www.niwa.co.nz/our-services/online-services/uv-and-o...

And some explanation behind UV reporting: https://www.niwa.co.nz/our-services/online-services/uv-and-o...

That's a misconception, if I remember correctly. The ozone layer is over Antarctica. UV levels here (Australia) are high because the air is quite dry and clean (so I have heard). During summer (i.e. now) the UV index reaches 13 daily.

See the image: http://www.abc.net.au/science/articles/2008/09/17/2367117.ht...

It seems to vary over Australia but I'm not sure how far from the normal values this is

That's literally the first time I see that visualisation. Check this out:

Does the Antarctic Ozone Hole ever come over Australia?

    No. The ozone hole has only ever been observed to be well south of the Australian mainland and Tasmania. In fact, during springtime, when the hole is in existence, ozone levels over southern Australian cities are at their highest.

Source: Australian bureau of meteorology http://www.bom.gov.au/uv/faq.shtml

You can also check the Wikipedia page on the ozone hole, where the image showing the largest extent of the hole (2006) doesn't cover Australia

Source: https://en.m.wikipedia.org/wiki/Ozone_depletion