Nearly two months since a major storm brought widespread heavy snow and freezing rain to eastern parts of the US, a new winter storm is sweeping across north-eastern US states and south-eastern Canada.

An area of low pressure, which first developed in north-western parts of the US late last week, intensified rapidly as it pushed north-east through central parts of the US.

Combining dry, cold air from northern parts of the continent with warm, humid air from the tropics, the system generated a large area of snowfall that swept through the northernmost US states on Sunday, while a narrow band of heavy rain and thunderstorms – associated with a strong cold front – developed across a line stretching from the far north of mainland US to the Gulf of Mexico.

Strong, gusty winds fanned a large wildfire across Nebraska, burning an area of more than 550 square miles. On Sunday, the National Weather Service issued an outlook warning of tornadoes along the front, with a 15% risk assigned to an area home to more than 11 million people across three states for Monday.

As the new week begins, the storm centre will continue pushing north-east into south-eastern Canada, bringing heavy snowfall, freezing rain and strong winds to north-eastern US, Ontario, Quebec, and Newfoundland through Monday and Tuesday.

Impacts are likely to be most severe around the Great Lakes: snowfall accumulations of up to 60-80cm are expected, followed by winds of 60-70mph, producing blizzard conditions and significant drifting.

Meanwhile, the cold front farther south will sweep through the US east coast on Monday, ushering in a polar air mass that will drive temperatures 10-25C below the seasonal average across the eastern two-thirds of North America.

Sub-zero temperatures are likely to reach as far south as Alabama and Georgia. The coldest conditions in the US are expected in North Dakota and Minnesota, where temperatures may dip into the −20sC (−4F). Canada’s Manitoba and Ontario provinces may see temperatures fall close to −40C.

In contrast, the western third of the continent is likely to see temperatures soar 10–15C above the seasonal average – a sharp contrast which is not unusual across the US in late winter and early spring.

Elsewhere, Australia has seen very high rainfall in recent weeks. In parts of Queensland last week, a year’s worth of rain fell within 72 hours. Further rainfall is expected as a low-pressure system slides south-eastwards across the central swathe of Australia early this week before stalling over the tripoint border region of New South Wales, Queensland and South Australia. Up to 150mm in a 48-hour window is expected.

Flood warnings were issued last week and will remain in place across much of the Australian interior.