Power cuts, sizzled tennis players and runaway grassfires featured in another scorching summer's day in and around Sydney, with only a limited respite before the heat returns.

Sydneysiders are in for a roasting as high temperatures combine with rising humidity to make for an exceptionally uncomfortable day.

It was a tough call as to who had the more enviable job. The answer depended which end of a large and potentially dangerous predator you would rather be working on: the head (read canine teeth) or the tail (read anal gland).

A spectacular cloud formation captured during a flight over the Great Australian Bight has delighted weather enthusiasts and enraged conspiracy theorists.

Health authorities have warned Sydneysiders to be on alert as the baking sun sends temperatures and ozone levels soaring and triggers a total fire ban.

One hundred and thirty-seven years ago, well before the Calaveras North Grove was purchased by the California State Park System and renamed the Calaveras Big Trees State Park, the land's owners carved an enormous hole in the base of one of its sequoia trees. On Sunday, that tree fell.

NSW Health has issued an air pollution alert as Sydney prepares to swelter through another summer day, warning residents that an increased level of ozone in the atmosphere is likely to affect residents with respiratory problems.

Canberrans who have stepped outside and felt particularly sweaty these past four days can blame the mercury for hitting 30 degrees or higher since Friday. And they may not get some relief for at least another week.

Plans by the Baird government to overhaul the state's mining approval process have drawn the ire of anti-coal groups and wary support from the industry.

Sydneysiders face an extended period of hot weather with warm nights likely to give only limited relief from daytime heat peaks.

• COMMENT

Growing up in Pakistan, my favourite show was Flipper. Living in a city a thousand kilometres from the nearest ocean, it was the most I knew about our beautiful dolphin friends.

The first band of what forecasters predict will be the region's most powerful storm in a decade moved into Northern California on Saturday evening, prompting official warnings of widespread flooding and epic snowfall in mountain areas.

A stubborn heatwave is settling in across the state with little relief in sight for days.

SeaWorld San Diego is ending its long-running killer whale show after years of outcry and falling attendance prompted it to renounce theatrical orca displays.

Melbourne Renegades defend the decision to hang two giant JumboTron screens above the arena for Saturday night's Big Bash League derby.

An enormous rift in one of Antarctica's largest ice shelves grew dramatically over the past month, and a massive chunk could break away as soon as later this summer, British scientists reported this week.

Tilikum, the killer whale featured in the documentary "Blackfish" that made the case against keeping orcas in captivity died on Friday, SeaWorld officials said.

A spill of heavy fuel oil in Sydney Harbour raises fresh concerns from local residents about the safety of Australia's oldest storage depot.

Most of NSW will endure heatwave conditions from now until at least the middle of next week as a hot air mass moves in from central Australia.

If you want to save an elusive porpoise from being wiped out forever, why not try a team of dolphins, specially trained by the US Navy to detect undersea mines?

He was quite the catch: young, good looking and fit. Spotted lounging in a tree not far from the edge of a road, this koala was a welcome addition to a study which hopes to shed light on why the Somers koala population is in decline.

Sydney will get its first burst of summer heat in 2017 starting from the weekend, as dreary conditions make way for the sun.

Australia posted its fourth-hottest year in 2016, driven by record sea-surface temperatures around the nation, in a period marked by frequent extreme events, the Bureau of Meteorology said.

Chickens are just as intelligent as many of their feathered friends and demonstrate thinking skills on par with mammals and primates, a US scientist has discovered.

Evidence the earth saw a slowdown in global warming over the past couple of decades has been further eroded

To the uninitiated they don't look like much to get excited about. Perhaps the only intriguing thing is that their bulbous bodies are a milky-white, rather than dark brown or black. But these tadpoles are special.

"It feels like you are at the centre of the Earth."

A time-lapse video of smog rolling into Beijing offers a jarring new perspective of the pollution that has been afflicting the Chinese capital in recent months.

If solar panels topped Suncorp Stadium, the Queensland Performing Arts Centre and Roma Street Station, they could generate electricity for 1200 homes and save 5414 tonnes of carbon emission a year.

First came the clouds of mosquitoes, then the swarms of flies and now insect experts are warning that teams of termites could be hard at work in homes across Melbourne.