Tomorrow is the summer solstice! Here’s what that means

Adelaide is officially welcoming summer this week, with the arrival of the summer solstice, the longest day of the year! The precise astronomical moment occurs at 1:33am ACDT, Monday, December 22nd, marking the point when the Southern Hemisphere is tilted most directly towards the sun, meaning it’s the greatest amount of daylight Adelaide will see all year.

Before you say it already feels like summer never ends in December, this time, there’s science to back it up. On solstice day, Adelaide can expect around 14.5 hours of daylight, giving locals an extended window of time to enjoy the sunshine from early morning through to a long evening. And for those lucky enough to already be on Christmas break, it’ll be the kind of day perfect for getting outside and enjoying those extra-long summer catch-ups.

The summer solstice is widely recognised as the official start of summer, even if the hottest days are still to come. While it might feel counterintuitive, the solstice itself isn’t usually Adelaide’s warmest day of the year. That title typically falls later, often nearer to the end of summer, thanks to a phenomenon known as seasonal lag. The land and ocean take time to absorb and radiate heat, meaning the highest temperatures follow weeks after the sun’s strongest positioning.

What the solstice does bring is an energy shift. There is more light, longer days and a sense that summer is properly underway. Astronomically, the solstice is the result of Earth’s axial tilt of around 23 degrees. While Adelaide enjoys its longest day, the Northern Hemisphere experiences its shortest, showcasing the balance of our planet’s seasonal rhythms. It’s a moment that has been observed and celebrated across cultures for thousands of years, often symbolising renewal, abundance and connection to nature.

While the solstice delivers the most daylight overall, it doesn’t align with the earliest sunrise or latest sunset. In Adelaide, the earliest sunrise actually occurs slightly earlier in December, while the latest sunsets arrive closer to the end of the month. These variations are part of what makes the solstice such a fascinating point in the calendar, even though it quietly happens while most of us are asleep.

So as we approach the summer solstice here in Adelaide, it’s a reminder to slow down, stay out a little longer and embrace everything this fantastic time of year brings. The solstice signals the beginning of an Australian summer defined by sunshine, outdoor living and that unmistakable festive feeling that comes with December.

For more information on the December Solstice, click here.