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Autumnal equinox almost here – what this means for Australia

Source Weatherzone Tue 17 Mar 2026

The Southern Hemisphere’s autumnal equinox will occur later this week, marking the date when day and night are roughly equal in length across Australia. What is the equinox? There are two equinoxes each year, one in March and another in September. Each equinox marks the moment the Sun appears to be positioned directly above Earth’s equator. This happens because Earth’s axis is tilted neither towards nor away from the Sun at the equinox. At all other times of the year, the Earth’s Southern and Northern Hemispheres are either tilted towards or away from the Sun. Image: Earth’s orientation relative to the Sun on the date of the equinoxes. Source: Weatherzone. Following the equinox in March, the Sun appears to become positioned above the Northern Hemisphere as Earth’s North Pole becomes tilted towards the Sun. By contrast, Earth's South Pole tilts away from the Sun after the March equinox. This year’s March equinox will occur at 2:46 pm UTC on Friday, March 20, which will be Friday night or early Saturday morning in Australia. Almost equal day and night Day and night are nearly equal in length for most places on Earth on the date of the equinox. However, the March equinox day is slightly longer than its night for two main reasons: Sunrise and sunset are defined as the moments the top edge of the Sun reaches Earth’s horizon at the start and end of each day. Because the Sun’s face is a large disc and not a single point, it takes several minutes for the face of the Sun to rise and set. This adds a bit of extra daylight at either end of the day. If sunrise and sunset were defined as the moment when the centre of the Sun reached the horizon, then day and night would be closer to equal length on the date of the March equinox. Earth’s atmosphere bends light. This means sunlight is visible even when the Sun is just below the horizon. For most places on Earth, day and night are closest to equal length a few days after the March equinox, on a date called the equilux. This year’s autumnal equilux will fall between March 23 and 29 for most of Australia. Following the equilux, nights will be longer than days in Australia for around six months, until the next equilux occur in late September. With the March equinox almost upon us, this also means that cooler temperatures and more wintry weather are on the horizon for Australia. - Weatherzone © Weatherzone 2026