Australian Weather

Today, 2:43AM UTC

It was an upside-down night of weather in Victoria, with the mercury hovering well above zero overnight across the higher parts of Victoria’s alpine region, while numerous locations near the coast were slightly colder for most of the night. For example, at 4 am this Tuesday, July 7: The ski resorts of Mt Buller, Mt Hotham and Falls Creek were 4.8°C, 3.5°C and 4.0°C respectively. Locations only a few metres above sea level like Melbourne Airport, Geelong and the Melbourne CBD were 2.9°C, 2.9°C and 4.6°C respectively. That’s right: the Melbourne CBD was colder at 4am on Tuesday morning than Mt Buller, the nearest major ski resort to the Victorian capital. Why the unusual disparity? The answer is that there was a strong temperature inversion. What is a temperature inversion? Image: 24-hour observations for Mt Hotham (Vic) with the orange temperature line showing how the mercury stayed well above zero all night. Source: Weatherzone. We all know that the atmosphere becomes colder as altitude increases (until you hit the stratosphere). That’s why it’s usually colder in the mountains than lower down. But sometimes, the temperature profile temporarily flips, with relatively cooler air near ground level sitting beneath a layer of warmer air. That’s called a temperature inversion, and it’s what occurred in parts of Victoria overnight. How do temperature inversions happen? One of the most common ways for a temperature inversion to develop is by radiative cooling of the air near the ground. This typically happens on clear and calm nights, when the ground gets colder at night when heat radiates into space. Clear and calm nights typically occur near the centre of a strong high pressure system – and it’s no exaggeration to say that southeastern Australia has one of those in place at the moment. Indeed, the high with a central pressure of 1044.5 hPa centred over Tasmania on Monday set a new provisional high pressure record for the Australian region. Relatively mild easterly winds played a part in the mild overnight temperatures in the Victorian Alps last night too. The influence of that Tasman Sea air contributed to an unusually warm layer of air forming from around 1500-2500m above the surface. Image: 850 hPa temperature and wind for Victoria at 7 am (AEST) on Tuesday, July 7, 2026. Source: Weatherzone. As the image above shows, temperatures at the air pressure level of 850 hPa in the atmosphere (an elevation of about 1500 m) were virtually the same in the Melbourne area as in the mountains to the northeast of the city. Most nights (without an inversion in place), you’d see a stark contrast. If you look closely at the wind barbs, the "feathers" show the southeasterly wind flow that contributed to relatively warm air at higher elevations. Winds were light, which meant the air in in the atmosphere couldn’t "mix" and prevent an inversion from occurring. What effects do temperature inversions have on surface weather? Apart from making the surface cooler than the layer of air above it, temperature inversions can also cause valley fog – and that’s what happened in parts of Victoria last night as the valley air condensed to its dew point, forming fog. Image: From about Geelong west, the 9 am satellite image showed cloud, but around Port Phillip Bay and greater Melbourne, as well as in the high country valleys in the state’s northeast, it was fog. Source: Weatherzone. One unwanted effect of temperature inversions at this time of year is that they prevent snowmaking at the alpine resorts, with overnight temperatures remaining too warm up high. Indeed, the 6:15 am Mt Hotham snow report began by saying "This morning we have a temperature inversion with the current temp sitting at a balmy +4.2 degrees." With the snowpack still very light for this time of year in the Australian Alps, temperature inversions are far from ideal for resorts looking to bolster their natural snowpack with snowmaking. Please check the Weatherzone snow page for the latest forecasts, live cam images and more throughout the 2026 snow season.

06 Jul 2026, 5:02AM UTC

A weather station in Tasmania has just recorded what could be the highest mean sea level pressure on record in Australia. According to data from the Bureau of Meteorology, a weather station at Ouse, Tas registered a mean sea level pressure of 1044.5 hPa shortly before 10 am AEST on Monday, July 6, 2026. This is provisionally the highest mean sea level pressure on record in Australia, beating the previous record of 1044.3 hPa at Launceston on June 7, 1967. Image: Weather observations from Ouse, Tas on the morning of July 6, 2026, showing mean sea level pressure reaching 1044.5 hPa at 9:50 am. Source: Weatherzone. What is mean sea level pressure? The term mean sea level pressure (MSLP) refers to the atmospheric pressure adjusted to Earth’s mean sea level at a given location. It is calculated by taking observed air pressure at the Earth’s surface and then adjusting it to what the pressure would be at Earth’s mean sea level. MSLP is commonly used by meteorologists because it normalises air pressure to a single level, allowing pressure systems to be compared and mapped across the planet on a synoptic chart. Areas of high MSLP are referred to as high pressure systems and are usually associated with calm and dry weather. Air descends towards the surface at the centre of high pressure systems, which is why the surface pressure becomes higher relative to the surrounding atmosphere. By contrast, areas of low atmospheric pressure – commonly referred to as low pressure systems – are characterised by rising air, low surface pressure and stormy weather conditions. Image: Modelled mean sea level pressure over Tas at 10 am AEST on Monday, July 6, 2006. Source: Weatherzone. Why was the air pressure so high in Tasmania on Monday? Monday morning's provisional mean sea level record occurred as the centre of a strong high pressure system sat directly over Tas. This high pressure system has been intensified by a deep low pressure system sitting over the Tasman Sea, due to a process called anticyclonic intensification: The low pressure system over the Tasman Sea rapidly intensified on Sunday and Monday while located to the west of New Zealand. Rising air inside this low moved away horizontally once it reached higher altitudes – a process called divergence. The air escaping the low’s upper levels flowed into the upper-levels of high pressure system – a process called convergence – where it then descended towards the surface – also called subsidence. How will this strong high pressure system influence the weather? The clear and calm conditions at the centre of the strong high pressure system caused bitterly cold temperatures on Monday morning. This included Melbourne dropping to 3.2°C, which was its coldest morning so far this year, while Coldstream hit -2.7°C. In Tas, Liawenee’s temperature plunged to -8.1°C shortly after 7 am on Monday morning. Monday’s provisional record-breaking high pressure also meant there was more air sitting above Tasmania. Compared to the global average mean sea level pressure of around 1013 hPa, Monday’s 1044.5 hPa meant there was about a 3% increase in air mass sitting above Ouse. So, if you were feeling a little weighed down on Monday morning, you can blame it on the extra air sitting above your head.