Seasons in the southern hemisphere

Sydney gets about 14 hours 25 minutes of daylight on 21 December and about 9 hours 54 minutes on 21 June.

Same tilt, opposite seasons

When the north end of Earth's axis leans towards the Sun, the south end leans away, so the two hemispheres always have opposite seasons. December brings the longest days and the highest noon Sun to Sydney, Cape Town and Buenos Aires, and June brings their shortest days. In the model, set the latitude to 34° S and the chart flips: the peak moves to December and the trough to June. Christmas in Australia falls in early summer.

Names follow the local season, not the calendar of the north. In Australia the December solstice is the summer solstice and the March equinox is the autumn equinox. Weather services in both hemispheres also use meteorological seasons, whole calendar months grouped in threes, because they make records easier to compare. NOAA and the UK Met Office count northern summer as June, July and August. Australia's Bureau of Meteorology counts summer as December, January and February, winter as June to August, and starts its seasons on 1 March, 1 June, 1 September and 1 December.

Does perihelion make southern summers hotter?

Here distance does make a small difference. The southern summer comes in December and January, right around perihelion, so the southern hemisphere receives about 7% more sunlight at the top of the atmosphere in its summer than the north does in its summer. You might expect much hotter southern summers, but the effect is softened. The southern hemisphere is mostly ocean, and water heats and cools slowly, so it smooths out the difference. The Bureau of Meteorology notes that the oceans around Australia also delay the seasons: in southern Australia the warmest week usually comes in late January or early February, weeks after the solstice.

Seasons of different lengths

Earth moves fastest around perihelion and slowest around aphelion. That makes the astronomical seasons unequal in length. Using the 2025 and 2026 dates from timeanddate.com, the time from the December 2025 solstice to the March 2026 equinox was about 88.99 days, while the time from the June 2026 solstice to the September 2026 equinox was about 93.65 days. So the northern winter, which is the southern summer, is the shortest astronomical season, and the northern summer (southern winter) is the longest.

The southern hemisphere also has the tropics, polar circles and climate groups described in the earlier units, mirrored. The Tropic of Capricorn crosses Australia, southern Africa and Brazil; the Antarctic Circle surrounds almost all of Antarctica, which has long polar nights in June and July. Ushuaia in Argentina, at about 54.8° S, has roughly 17 hours 20 minutes of daylight in late December and about 7 hours 12 minutes in late June, close to the numbers for a city at 55° N with the months swapped.