Severe thunderstorms and cold fronts hit the south eastern part of Australia

Earlier on Monday, a freak thunderstorm hit Sydney, causing temperatures to drop by 10 degrees as winds were recorded at 82km/h at Sydney Airport.

The Bureau of Meteorology forecast thunderstorms up the coast of NSW all the way to Newcastle for Monday.

Meanwhile in the Australian Capital Territory, there were thunderstorms beginning at 2am on Monday, moving into the early morning commute.

The wind and rain was so intense a tree fell onto a car at Glenloch Interchange, blocking traffic about 100 metres from the off ramp from Caswell Drive onto Parkes Way.

The tree was eventually cleared by 11am.

Meanwhile, parts of Victoria could expect snow with BoM releasing a statement on Sunday warning people of the cold to come.

So why is this weather so weird? We can mostly blame La Nina.

In BoM's latest seasonal streamflow forecasts, high streamflows are likely for December to February along the east and south-east coast of the mainland and for Tasmania.

"La Nina is likely to continue until early 2023. The Southern Annular Mode (SAM) index is weakly positive and likely to be neutral to positive through December," BoM said.

"The current long-range forecast for wetter-than-average eastern Australia and drier-than-average western Australia reflects these drivers and the warmer than average sea surface temperatures around Australia."

Meanwhile, northern Australia is experiencing the opposite climate, with a heatwave expected to ease this week.

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But it's likely those in southern Australia will be experiencing much cooler temperatures than usual as the cold front covers most of the southern east, which BoM anticipates to be "even colder from mid-week with another cold front".