Australian Weather

24 Apr 2025, 11:42PM UTC

April 25, 1915, is the date that the Anzacs began the Gallipoli Campaign. However, the original plan was for the invasion to begin at dawn on April 23. Bad weather caused a two day delay. The weather models and data that we take for granted today did not exist in either of the world wars and it was very difficult to create weather charts or make accurate forecasts even within a day. Today we can even use weather models to look back in time and see what the bad weather was that delayed the Gallipoli Campaign. On the 23rd sustained winds were blowing from the north-northeast at about 40km/h over the Aegean Sea between Greece and Turkey. This wind would have been a headwind and would have been producing waves of 1-2m.  Image: near surface winds on April 23, 1915 (m/s). Source: NOAA. These winds were produced by a pressure gradient between high pressure over eastern Europe and Russia and low pressure over Turkey. Image: Sea level pressure (SLP) anomaly on April 23, 1915. Yellow/Orange shows higher than normal pressure and blue lower than normal. Source: NOAA. A similar pattern is being forecast for next Monday, 28th April 2025. Note how tightly the isobars are packed across Turkey. Image: Mean sea level pressure on the morning of Monday, 28th April 2025 according to the ECMWF model. The sustained winds are forecast to be from the northeast at about 40-50km/h, similar to what would have been present on April 23, 1915. Image: sustained winds (knots) over the Aegean Sea at about dawn on Monday 28, 2025 according to the ECMWF model. Back to 1915. By dawn of April 25 the high pressure over Europe and Russia had weakened, reducing the pressure gradient across Turkey. This led to a weakening of the winds to about 20km/h, allowing the Anzacs passage from the island of Lemnos, Greece to the coast of western Turkey. Image: near surface winds on April 25, 1915 (m/s). Source: NOAA. In the second world war, the weather would play a similar but much greater role in the timing of the D-Day invasion. You can read about how a British forecaster was able to predict a break in the severe weather that determined D-Day: D-Day - the most important weather forecast in history - Met Office.

24 Apr 2025, 6:06AM UTC

The National Anzac Day Dawn Service on the Parade Ground of the Australian War Memorial in Canberra is a solemn occasion which is televised nationally. It also happens to be one of the chilliest dawn services anywhere in the country. And that got us thinking: how cold can Canberra get on Anzac Day? Canberra’s lowest Anzac Day temperature on record was in 1999, when the mercury fell to a frigid –3.7°C. That remains the capital’s lowest reading on any day in April. Anzac Day 2024 in Canberra was another chilly one, with a minimum of –0.5°C. READ MORE: A digger's letter from snowbound Gallipoli But Anzac Day in Canberra does not always begin with freezing conditions. Indeed, the capital’s average April minimum is 6.8°C, while its average on Anzac Day since 2009 (at the current Canberra Airport official weather station) has been 4.7°C. This year has been a good example of typical April variation in Canberra, with one night below freezing to date, and several nights so far where the minimum stayed in double-digit temperatures. As for Anzac Day 2025, it’s set to be one of the mild ones by local standards, with a minimum around 9°C ahead of a balmy day with a top of 24°C. When does Canberra’s first frost occur each year? While Anzac Day itself in Canberra is not always frosty, local lore holds that the city’s first frost of the year usually occurs around Anzac Day. Is this accurate? It’s actually a little earlier. In order for frost to form on grass, the temperature usually only needs to be as low as about 2°C. That’s because the standard Stevenson screen height (the box holding meteorological instruments) is 1.2 metres above ground level, and the ground tends to be significantly cooler than the air immediately above it. So to calculate the date of Canberra’s first frost, you need to find the average date of the first night with a minimum of 1.8°C or lower. Based on a small sample of records going back to 2008, the average date of the first night with a minimum temperature of 1.8°C or lower has been April 13. This sample size is too brief to be scientifically robust, but it’s still an indication of the date of the first frost in recent times. Image: Minimum temperatures across Australia on Anzac Day, 1999, when Canberra had its coldest April 25 on record. Source BoM. As for the coldest Anzac Day temperature on record anywhere in Australia, it must be stated that the BoM only publishes climate extremes dating back to 1957, but in the 68 years since then, the chilliest Anzac Day reading was –8.4°C at Cooma Airport in 1999. For those interested in the coldest temperature ever recorded in Australia on any day in April, it was –13°C at the small ski village of Charlotte Pass, NSW, on April 29, 2009. Charlotte Pass also registered Australia’s coldest night on record (any month) with a bone-chilling –23°C on June 29, 1994. Weatherzone would like to take this opportunity to express our respect and gratitude to all Australian servicemen and servicewomen, past and present. Lest we forget. READ MORE: From scorching heat to snow: the extreme weather of Gallipoli