Spring scorcher to follow record warm winter for south-east capitals

Australia is experiencing an extremely mild winter, leading to projections of record-breaking heat in spring. Sydney and Melbourne have both set records for the warmest winters on record, with mean temperatures above all previous years since the 1850s. Canberra had its highest-ever winter temperatures, while Hobart's winter ranked second warmest.

Adelaide and Brisbane's winters will rank third warmest on record. The consistent above-normal temperatures in winter have created a climate similar to northern regions. For instance, Sydney's winter mean of 15.3C was only slightly below Brisbane's historic winter climate from the last century. Hobart's winter mean of 10.4C equaled Melbourne's long-term winter average, while Melbourne's 12.2C was just 0.8C shy of Sydney's historic winter climate.

Another notable aspect of this winter was the absence of extreme cold days and snow. Brisbane recorded only two maximum temperatures below 20C, and Canberra had only one below 10C. Canberra's coldest day this winter, a high of 9.5C on July 13, was the highest ever and 3C warmer than the city's typical coldest day. Sydney's lowest maximum was also a record at 15.5C on June 25, 3.6C above the norm.

The lack of polar outbreaks this winter resulted in sparse snowfall, affecting alpine and sub-alpine regions. Perth's west coast remained relatively cool compared to the eastern states, with temperatures only 0.3C above the long-term average. The root cause of this year's abnormal heat is a mix of natural variability, climate change, and a strong El Niño event.

This heat pattern is expected to continue through spring, with warm north-westerly winds setting in early September, delivering temperatures up to 5C above normal. By the first day of spring, cities like Canberra, Melbourne, and Adelaide are expected to hit record highs of 21C, 22C, and 22C, respectively. Sydney is forecast to reach a record 27C, and Brisbane 31C, both about 7C above the long-term average.

The upcoming weeks are likely to bring even more warmth, with temperatures up to 7C above normal along the east coast. Modeling suggests that the next three months will be the warmest on record for an Australian spring in southern states. The BOM's ACCESS-S model predicts southern Australia will see temperatures between 2C and 3C above the 1981 to 2018 average, which translates to 3C to 4C above pre-industrial levels.

The likelihood of temperatures being in the top 20 percent of years for maximums is greater than 80 percent, while for minimums, it's even more widespread, covering around two-thirds of the country. Forecasts for early summer show no respite, with a multi-model prediction for January indicating a forecast anomaly of 1C to 2C across most of Australia.

While the baseline used is a warmer 1993 to 2016 period, converting this to pre-industrial levels would increase the prediction by another 1.2C.