Sydney has officially experienced its hottest June since records began in 1859, after a winter month that felt more like spring - because of course it did.

The Bureau of Meteorology confirmed on Friday that June 2026 broke the all-time mean temperature record at Observatory Hill, where tracking first began in 1859. The month featured 15 consecutive days with a maximum temperature of at least 20°C between 7 and 21 June, smashing the previous June record of nine consecutive days set in 1919.

Sydney’s overall mean temperature hit a record-breaking 16.1°C, eclipsing the previous 1991 record of 15.7°C. The average maximum (20°C) and minimum (12.2°C) each ranked as second-highest on record individually, but their sustained consistency secured June 2026 as the warmest overall.

Prof Andy Pitman, a Sydney-based climate scientist, expressed a “complete lack of surprise” at the new record. “It’s got the signature of global warming all over it,” he said. “With temperature, there’s no wriggle room around it any more … We know that the warming is due to the failure of governments around the world to deeply cut emissions.”

Experts pointed to record-breaking ocean temperatures off the NSW coast as the culprit. Prof Matthew England, an oceanographer at UNSW, said the ocean has become a global “warming hotspot” experiencing rapid temperature increases. “The basic balance in our climate system is that the oceans absorb a lot of heat during summer and they radiate that heat back into the atmosphere during winter,” he explained. “Those very warm oceans off Sydney would be a significant contributor to the record warmth we’ve had this winter.”

Normally, southerly winds bring cold temperatures to the coast, but as they pass over the abnormally warm Tasman Sea, they absorb the ocean’s surface heat, blunting their chill by the time they reach Sydney. On land, Pitman noted that vegetation that should be dormant during winter was “happily transpiring,” drawing moisture out of the soil and amplifying heating due to CO2. “The big issue here is not that lots of people in Sydney are enjoying a warm winter. It’s downstream in spring and summer, when everything is drier than it should have been,” he warned.

While a milder winter might feel pleasant, England cautioned that “the actual cost of high-end events is severe. People can kind of be lulled into a false sense of security.” Looming heatwaves and bushfire risks will be heavily amplified by El Niño shifting moist air away from eastern Australia. With a recent NSW Net Zero Commission report highlighting severe gaps in climate adaptation, Pitman urged immediate action. “The climate science community have been warning about this since at least 1995,” he said. “Serious contingency planning needs to be in place for extreme heat. I don’t think Australia is prepared for the kind of heat it’s likely to experience.”

The unseasonal warmth extended across greater Sydney: of the 16 weather stations with at least two decades of data, every single one recorded either an all-time high average maximum temperature or a 20-year peak. And it wasn't just NSW - according to Weatherzone, Melbourne, Brisbane, and Canberra all had one of their top five warmest Junes on record in 2026.