A warm start to winter reflects global extreme temperature trends driven by climate change
Many regions across Australia have already surpassed early winter maximum temperature records.
In southern Australia, Sydney and Melbourne experienced their warmest-ever winter onsets. Daily data indicate both cities recorded above-average June temperatures nearly every day of the month.
Adelaide also reported above-average June temperatures. Hobart and Canberra had mild winter beginnings with temperatures significantly above normal. Perth remains the only southern capital city with typical June temperatures.
Globally, unseasonably high temperatures attributed to global heating are being observed, including the recent heatwave in western Europe and parts of Asia.
What can be anticipated for the remainder of the winter season? And what implications does a warm winter have for Australia’s forthcoming summer?
The months ahead
According to the Bureau of Meteorology’s outlook, abnormally warm conditions in Australia are expected to persist for at least the coming weeks. Extended dry spells are likely, particularly in late winter and spring, following the recent dry period.
Nonetheless, occasional cold polar air outbreaks may still affect southern Australia due to the jet stream’s
"waviness"south of the continent. Waviness refers to the meandering of air currents forming the jet stream. When this waviness occurs in a north-south direction rather than west-east, it can influence the movement of cold air masses and low-pressure systems.
The 2026 snow season has commenced poorly, with forecasts indicating an unfavorable outlook for sufficiently deep snow cover. However, a single or a few unexpected heavy snowstorms could significantly alter the season’s trajectory.
We’re part of a wider trend
The current Australian seasons exemplify a global pattern of unseasonably high temperatures, including the early summer heatwave in Europe.
Historically, extreme summer temperatures in Europe occurred later in the season, typically in July or August. However, the recent heatwave produced record June maximum temperatures across Europe.
On 26 June, the UK’s
"temperatures reached 37.3°C", surpassing the previous all-time UK June record of 36.1°C set in 1976. During this heatwave, much of France, Spain, Italy, and Germany recorded or exceeded 40°C. High humidity levels accompanied these temperatures. This unusually early and intense heatwave confirms that climate extremes have become the new normal.
Many countries are experiencing their warmest winters on record. This extreme heat is attributed to
"global warming since the 1990s caused by human-made climate change". The United Nations forecasts that hot and cold extremes will affect nearly all inhabited regions with increasing frequency.
A study published earlier this year confirmed that this unseasonable warmth results from the warming of Earth’s atmosphere and oceans. Global warming alters large-scale southern hemisphere atmospheric circulation patterns and intensifies the effects of known
"climate modes", which are large-scale atmospheric and oceanic processes that govern weather patterns and climate variability.
It is established that southern hemisphere jet streams — fast-flowing, narrow bands of wind in the upper atmosphere — and associated storm tracks have shifted poleward. Previously reliable winter and spring rain-producing systems now frequently bypass southern Australia.
Consequently, southern Australia has experienced an increase in high-pressure systems, leading to cloudless skies and elevated daytime temperatures. This pattern is similar to the current situation in western Europe.
Additionally, Pacific Ocean temperatures off Australia’s subtropical east coast are significantly above average. As a result, Tasman Sea high-pressure systems are directing warm, humid air over southeast Australia, contributing to warmer-than-average daily minimum temperatures.
A record-setting Australian summer?
Questions arise regarding whether Australia’s upcoming summer will break heat records. Presently, the most accurate response is a cautious
"maybe".
Accelerated global warming continues and is not limited to Europe. Recently, the eastern half of the United States issued an excessive heat warning.
Forecasters advise that southeast Australia should anticipate
"above-average temperatures and dry conditions"during this El Niño year — a concerning combination that suggests the likelihood of record heatwaves, droughts, and extreme bushfire risk.
Melbourne is especially vulnerable to dry conditions due to its catchment status. Its water catchment level, currently at 64% and declining, is the lowest since the 2017–19 drought. Observational data indicate Melbourne missed the rainfall that replenished other southern capital cities during autumn and spring; the city and its catchment lie in the rain shadow of the Great Dividing Range, which reduces moisture from warm, humid subtropical air.
There remains a possibility that Australia’s summer will not break records. El Niño does not invariably produce extreme temperatures, dry conditions, and fire weather. Furthermore, the
"Southern Annular Mode", a climate driver influencing Australian rainfall and temperature, might bring increased cold fronts.
Therefore, extreme heat may not materialize in late spring or early summer. However, current trends suggest it is likely.
Milton Speer is a visiting fellow at the School of Mathematical and Physical Sciences at the University of Technology Sydney. Lance M Leslie is a professor at the School of Mathematical and Physical Sciences at the University of Technology Sydney.
