Melbourne is bracing for flooding as a huge storm moves across the state, with falls of 50 milimetres in the city's north-east suburbs likely on Saturday morning.

Hume Coal’s mine and rail project applications have been referred back to the Independent Planning Commission for a public hearing and determination within 12 weeks.

Gusty winds buffeted parts of Sydney late on Tuesday as a band of dry thunderstorms moved across parts of eastern NSW.

If Thursday hits its predicted peak it will be the ACT's longest March heat spell on record.

Global temperature records continue to tumble, with August easily the hottest in 124 years of data, Japan's Meteorological Agency says.

Sydney's late-summer spell of unusual warmth shows little sign of making way for autumn with another week of mild to hot weather ahead.

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The Bureau of Meteorology has issued a severe thunderstorm warning for parts of Sydney.

Residents in north-eastern NSW advised not to travel as heavy rains from another east coast low lift flood risks all the way down to the Hunter.

A broad and unpredictable trough stretching across south-east Australia could inundate Canberra with a month's worth of rain this weekend.

Temperatures are set to climb towards 40 degrees in coming days in Sydney's west with only cooling sea breezes likely to cap the mercury in the city.

Canberrans will face one of the worst fire danger days of the bushfire season on Tuesday as the temperature soars past 30 degrees amid dry, windy conditions.

Parts of Canberra have received more than the city's June average rainfall in less than two days with more rain on the way.

The impacts of the monster El Nino in the Pacific are likely to intensify across much of Australia, including worsening drought and an elevated bushfire threat, after conditions that were nullifying its effects suddenly retreated.

A "strangely warm southerly" is sweeping across Sydney today with little relief from the heat at beaches in NSW and Queensland because of Cyclone Winston causing large, dangerous and powerful surf.

Broken Hill's water reserves are down to about 4 per cent amid forecasts the town will be without water by the end of the year.

Destruction of more than 200,000 hectares of threatened species habitat has been approved by the federal government in the past decade, a report shows.

The state's second east coast low in as many weeks is likely to bring further heavy rains to north-eastern NSW but largely skirt flood-hit areas around Sydney and the Hunter Valley, meteorologists say.

Winter's grip will finally feel like it's loosened amid a "heat spike" this weekend - even if that season's squeeze was not a very tight one.

Hundreds of homes have been evacuated in southern California as heavy rains and wind lash the drought-stricken area.