Australian Weather

12 Sep 2025, 1:14AM UTC

There's still a healthy snow depth of almost two metres at the highest reaches of the Australian alpine region as we near the end of the second week of September. NSW hydro-electricity operator Snowy Hydro took its latest readings at its three NSW sites on Thursday, September 11, with a depth of 196.9cm at Spencers Creek – at an elevation of 1830m roughly halfway between the two major NSW ski resorts of Perisher and Thredbo. Image: Snow depth in 2025 (dark blue line) compared with 2024 (light blue line) at Spencers Creek, NSW. Source: Snowy Hydro. The latest reading means that the Spencers Creek snowpack has reduced in depth by about 10% from the previous measurement of 220.4cm on September 1. That early September reading now appears likely to be the season high, although it’s worth noting that the 2022 peak of 232cm was recorded on September 20, which was very late in the season. A typical spring week with a couple of twists In many ways, the past week has been typical for early spring in the high country of NSW and Victoria. There was a significant burst of rain, there were relatively mild maximum temperatures that reached at least a few degrees above zero most days, and the snowpack became coated in airborne dust from regions far west of the mountains, which often happens in September. Image: Dust from Australia’s interior on the snow on the slopes of Thredbo, NSW, before fresh snow started falling and covering it later in the day on Wednesday, September 10, 2025. Source: Rusty J via ski.com.au. But there were a couple of moments that stood out as somewhat unusual. Firstly, the 15cm or so of snow that accumulated from Wednesday afternoon into Thursday morning in the Snowy Mountains of New South Wales fell in rare, near windless conditions more reminiscent of the snow that often floats down in relatively still conditions in many overseas ski towns. Image: Fresh snow on the morning of Thursday, September 11, 2025, at Charlotte Pass, NSW. Source: "Fozzie Bear" via ski.com.au. This snowfall occurred when moisture drifted over the Snowy Mountains from the north and east, associated with the strong low pressure system that drenched parts of NSW. This is a relatively uncommon direction for snow-bearing moisture in the Australian high country, and when it happens, Victoria tends mostly to miss out, as happened this week. The second unusual occurrence was a slab avalanche on a steep part of Perisher ski resort, which was triggered by an expert skier. This type of avalanche can be very dangerous, however this one was fortunately quite small with no injuries reported. READ MORE: Two different stories about Australian avalanches from the big snow year of 2022 As for this coming weekend, breezy conditions are expected in the high country with the chance of light showers or possible snow showers at the highest elevations on Sunday. The major resorts of Mt Buller, Mt Hotham, Falls Creek (Vic) and Perisher, Thredbo and Charlotte Pass (NSW) all still have the majority of their lifts open. If you're heading to the mountains, don't forget to check the Weatherzone snow page for the latest forecasts, live cams and more.

11 Sep 2025, 7:06AM UTC

The likelihood of La Niña occurring in 2025 has increased due to a change in the way the Bureau of Meteorology calculates sea surface temperature anomalies in the tropical Pacific Ocean. What is La Niña? La Niña refers to a distinct pattern of sea surface temperatures across the tropical Pacific Ocean. When La Niña is occurring, it affects weather patterns on a global scale. La Niña occurs when cooler than average water develops at the surface of the central and eastern equatorial Pacific Ocean, and warmer than average water sits at the surface of the western tropical Pacific Ocean. This pattern of sea surface temperature anomalies typically enhances cloud and rainfall over the western Pacific, including parts of Australia. It also changes how weather behaves in other parts of the world. Image: Typical global impacts of La Niña during the Southern Hemisphere’s summer (December to February). Source: NOAA How is La Niña measured? The primary method for monitoring La Niña is to calculate sea surface temperature anomalies in a region of the central equatorial Pacific Ocean known as the Niño-3.4 region. Image: Niño 3.4 region. When sea surface temperatures in the Nino 3.4 region are sufficiently cooler than average for several consecutive months, La Niña is underway. According to the Bureau of Meteorology’s thresholds, the Niño 3.4 index needs to be lower than -0.8°C for three consecutive months for La Niña to be occurring. La Niña in the modern climate The Bureau of Meteorology has just changed the way it calculates sea surface temperature anomalies for monitoring La Niña (and El Niño). Traditionally, sea surface temperatures inside the Niño 3.4 region were compared to the long-term average of the 30-year period from 1991 to 2020. The difference between the current temperature and the long-term average temperature gave us the anomaly used for monitoring La Niña. However, rising global ocean temperatures caused by climate change have made this method ineffective. Put simply, Earth’s oceans are warming so quickly that the average ocean temperature of the past 30 years is cooler than the current global ocean temperature. This makes Niño 3.4 index values artificially warm when calculated using the traditional method. Instead of comparing the current state of the ocean to a baseline from the past climate, scientists have developed a new method that also incorporates the current average temperature of the global tropical oceans. This new method, with is called the relative Niño index, removes the climate change signal from the equation and makes it more useful in our rapidly warming climate. What is La Niña doing now? Based in the relative Niño index, forecast models suggest that the Niño 3.4 index will hover around -0.9°C to -1.0°C for the next three months, with a 45 to 75% chance that it will stay below the -0.8°C threshold needed for La Niña. Image: Niño 3.4 index forecast for the next 5-6 months. Source: Bureau of Meteorology. While La Niña was unlikely to occur in 2025 using the now old method of calculating ocean temperature anomalies, it is now more likely in 2025 based on the relative Niño index. Australian seasonal outlooks are reflecting the influence of a developing La Niña signal, with above average rain predicted over large areas of the country’s north and east during the last three month of 2025. Image: Rainfall outlook for October to December 2025. Source: Bureau of Meteorology. The increased cloud cover and rain associated with the potential La Niña may also help suppress daytime temperatures over parts of eastern Australia during late spring into early summer.