Today is the first day of spring in Australia 🌸🩷 "Spring has sprung, at least in Australia where the calendar ticking over to September means a change in the season. But not everywhere follows the same system. While Australia charts the seasons based on the Gregorian calendar, countries like the United States use significant points in the Earth's orbit around the Sun to define the changes. Here's what that means. When does spring start in Australia? Today — September 1. That's because we chart the seasons based on the meteorological system. The Bureau of Meteorology (BOM) says Australia follows this system for two reasons: It can track our temperature changes more closely It makes it easier for compiling and presenting climate data But this isn't the only way seasons are organised. And some places like the US and UK follow the astronomical season convention. Meteorological vs astronomical seasons Meteorological seasons are determined by annual temperature cycles and dates on the Gregorian calendar. Every year, the seasons roll over on the same date: Summer: December 1 Autumn: March 1 Winter: June 1 Spring: September 1 Whereas astronomical seasons are defined by the position of the Earth in relation to the Sun.