Another burst of wintry cold is heading Sydney's way - but not before the mildest run of weather so far this month.

Sydney's main reservoir will begin spilling on Thursday, leading to minor flooding downstream, the Bureau of Meteorology says.

Sydney is in for another scorcher on Thursday with the potential for 40 degrees over much of the city ahead of a gusty cool change from the south.

An Australian credited with creating a technique that has helped reforest millions of hectares of degraded land globally has won the 'Alternative Nobel Prize'.

It's the time of the year when the surf looks its most inviting, but it's also when our anxiety about sharks hits its peak.

There's nothing like a double rainbow to get Sydneysiders to wax lyrical (or resort to multiple exclamation marks!) 

You survived Melbourne's hot summer? Expect Autumn to be wet. But first, we have to get through March, which is looking like a scorcher.

Wild weather across the country has claimed three lives following three incidents of cars being swept away in flood waters.

Heavy snowfalls over the central ranges all the way up to New England are causing traffic chaos on NSW roads, with the Hume Motorway closed in both directions as wild weather heads towards Sydney.

Sydney will likely endure scorching temperatures into the 40s on Friday as powerful westerlies blowing from Australia's red hot centre block cooling sea breezes.

After the coolest winter in years, the mercury is ready to rise, forecasters say.

NSW will experience more frequent and longer heatwaves in the future as the climate warms with the worsening extremes dependent on whether carbon emissions continue to climb, according to research from the government and the University of NSW.

As Sydney's run of abnormally warm and dry conditions rolls into a sixth week, the first signs of break in the weather are showing up in the forecasts.

The rainy weather may have forced most Canberrans to spend the weekend indoors, but when the clouds clear snow-seekers can look forward to the first big snowfalls of the season thanks to a cool change expected later in the week.

A major climate summit of more than 190 nations was set to run overtime as delegates struggled to narrow gaps on guidelines to reduce greenhouse gas emissions and raise aid for developing nations.

Sydney's run of exceptionally chilly mornings will take a break for a few days but a return to sustained milder conditions may be weeks away.

Waking to 20cm of fresh snow, 10-year-old Brooke Stanton was ready for her first snowball fight of the day as the sun rose over Oberon, lighting up a town blanketed with its heaviest snowfall "in 40 years". 

Sydney is due one more lashing from the powerful low pressure system hovering off the NSW coast that earlier caused flooding in regions south of the city including the evacuation of hundreds of primary school students.

A 25-year-old Thai sea turtle died from blood poisoning on Tuesday, never recovering from an operation to remove 915 coins from her stomach, thrown into her pool for good luck, veterinarians said.

The meteorologists are calling what many Sydney commuters already know: autumn has arrived.

Global temperatures leapt in February, lifting warming from pre-industrial levels to beyond 1.5 degrees, and stoking concerns about a "climate emergency".

If you prefer your ocean temperature on the warm side, you had better get in quick for a final swim.

The El Nino in the Pacific Ocean is likely to affect Australia's climate for the rest of the year, according to the Bureau of Meteorology.

Three motorists have died in the floodwaters following the NSW storms.

Homes on Sydney's northern beaches have been partially washed away in the violent storms that battered the NSW coastline over the weekend.