The seven days from now until next Tuesday will be the darkest week of the year across Australia.

The Southern Hemisphere’s winter solstice will occur on Saturday, June 21, marking Australia’s shortest day and longest night of the year based on sunlight hours. Counting the three days on either side of the solstice date gives you the seven-day period with the least amount of daylight during the year.

Australia’s darkest week of 2025 will run from Wednesday, June 18 to Tuesday, June 21.

What is the winter solstice?

The winter solstice marks the date on which Earth’s Northern or Southern Hemisphere reaches its furthest tilt away from the Sun. Each hemisphere has a winter solstice spaced half a year apart. The Southern Hemisphere’s winter solstice occurs in late June and the Northern Hemisphere’s winter solstice occurs in late December.

When the Southern Hemisphere reaches its winter solstice, the Sun appears to be at its lowest point in the sky when viewed from south of Earth’s equator. This is also the shortest day of the year based on time between sunrise and sunset.

The table below shows the daylength for Australia’s capital cities on this year’s winter solstice.

Image: Daylength for Australia's capital cities on the date of the 2025 winter solstice.

Following the winter solstice on Saturday, days will start to become longer, and nights will become shorter across Australia. This trend will continue for six months until the Southern Hemisphere’s summer solstice on December 21-22.