Sydneysiders got down to cleaning up their damaged properties on Friday after destructive winds accompanying a sudden cool change broke up the 40-degree heat a day earlier.
The battering of the east coast came as the world recorded more freak weather events, including the first hurricane to form in the Atlantic in January since 1938.
The heaviest falls in Sydney on Thursday were recorded at Peakhurst in the south where 51 millimetres of rain fell. The city itself collected 34 millimetres up until 9am on Friday.
Winds linked to the thunderstorms reached 120 kilometres an hour, while parts of the city copped 90km/h gusts as the change moved through, Rob Sharpe, a meteorologist with Weatherzone, said.
Although the city was in for relatively cool weekend, he said, temperatures and the sunshine should start increasing by the start of next week.
Meterologists are busy updating their record books as the list of recent extreme weather events grows.
Hurricane Alex on Friday was heading for the Azores islands after forming over sea-surface temperatures much cooler than the 26 degrees usually required to trigger such a storm, according to the US National Hurricane Centre.
"It is very unusual to have a hurricane over waters that are near 20 degrees Celsius, but the upper-tropospheric temperatures are estimated to be around minus-60 degrees", creating the big instability, said Richard Pasch, a senior hurricane specialist at the centre.
There's certainly little shortage of above-average ocean temperatures, though, with the giant El Nino only now beginning to break down and most of the Indian Ocean setting record heat in 2015.
Preliminary figures from the Japan Meteorological Agency indicate last month was easily the hottest December for global land and sea-surface temperatures in data going back to 1891.
Compared with the average December for the 1981-2010 period, temperatures last month were 0.67 degrees above normal. The biggest previous discrepancy had been 0.31 degrees set only a year earlier:
Compared with the 20th century, global temperatures were 1.05 degrees above average, the agency said.
2015 as a whole set a new high mark for annual temperatures, major international agencies are likely to declare in the coming week. The warming influence of the big El Nino is coming on top of the background climate change, scientists say.
Non-government groups are already making that record annual call, with the Berkeley Earth group - originally set up to challenge climate science - declaring 2015 to be "unambiguously the hottest year on record".
Hurricane Alex forms in the central Atlantic - a rarity in January. Photo: NASA
The group said 2015 was 0.1 degree hotter than the previous warmest year in 2014 - a title it estimated was shared with 2005 and 2010. The latest heat leap should put to rest debate that there had been a pause or hiatus in warming. it said.
"This new high temperature record confirms our previous interpretation that the pause was temporary and that global warming has not slowed," Richard Muller, Berkeley Earth's scientific director, said.
Australia had its fifth warmest year in 2015, including a record hot final three months of the year, the Bureau of Meteorology said last week.
Elsewhere, the lower 48 states of the US had their second-hottest year on record, Berkeley Earth said.
By the group's estimates, 16.9 per cent of Earth's surface and 16.4 per cent of its land surface set record high annual averages in 2015:
Neville Nicholls, an emeritus professor at Monash University's School of Earth, Atmosphere and Environment, said the trend of the land warming faster than the oceans had been clear on for some time.
"The world's land areas are now, on average, more than a full degree warmer than they were in the mid-20th century, and more than 1.5 degrees warmer than they were in the late 19th century," Professor Nicholls said. "The warming over land shows no evidence of any slowdown."
"We need to plan for more warming, and for more frequent and more intense heatwaves, even if we can slow the rate of warming by reducing greenhouse gas emissions," he said.
Sydney, meanwhile, continued its clean-up on Friday after destructive winds accompanying a sudden cool change broke up Thursday's 40-degree heat.
The heaviest falls were at Peakhurst in Sydney's south, with 51mm of rain, Rob Sharpe, a meteorologist with Weatherzone, said. The city itself collected 34 mm up until 9am on Friday.
Winds linked to the thunderstorms reached 120 km/h, while parts of the city would have copped 90 km/h gusts as the change moved through, Mr Sharpe said.
While the city is in for relatively cool weekend, temperatures and the sunshine should start increasing by the start of next week, he said.
Another trough with associated low-pressure systems will move across the continent through much of the coming week, bringing widespread falls, the bureau predicts. (See its eight-day rainfall map below: