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