美国有线新闻 CNN 冰火两重天 美国极寒澳大利亚酷热（在线收听）

CHARLOTTE MORTLOCK: If Sydney's central business district reaches it's forecast maximum of 40 degrees today, it will be their hottest day since last summer, and 14 degrees above the average.

RYAN YOUNG: Here in Chicago, the temperature is nothing to play with. Dangerous lows, something the city hasn't seen in quite some time.

Look at the river. It's all frozen. It looks like a winter play land. Schools have been shutdown. Warming centers have been set up all across the city, and there's a real worry about the homeless population here, because if you're outside for any long period of time, frostbite has become a real concern. Out on Lake Michigan, it has been so cold you can see the steam actually rising.

CHARLOTTE MORTLOCK: This will go down in the books as Sydney's second hottest January on record. The sweltering haze has been put extra pressure on the in-demand power supply across the state, as many turn to fans and aircon in a bid to keep cool.

CARL AZUZ, CNN 10 ANCHOR: So a tale of two extremes leading things off for us today on CNN 10. But for the U.S. at least, relief is in sight and it will be a dramatic change. This week in Chicago, Illinois, temperatures dropped down to 25 degrees below zero Fahrenheit. But by the end of the weekend, the city's expected to see temperatures rise by 75 degrees, to the low 50s. Meteorologists expected Thursday to be the last day of extreme cold air in the US, at least temporarily.

That's when two-thirds of the country's population woke up to temperatures below freezing, and about a quarter of Americans shivered in temperatures below zero. A volunteer firefighter in Wisconsin emerged from battling a house fire with his beard covered in ice. The wind chill, which is what the temperature feels like when the wind blows, was negative 50. A popular phrase associated with U.S. mail carriers is, "neither snow nor rain nor heat nor gloom of night keeps them from their rounds".

But when artic temperatures frosted over the Midwest and Northeast, deliveries were suspended in parts of six states on Thursday. The Red Cross canceled hundreds of blood drives because of the cold weather, and in Michigan, a state that's used to weathering cold and driving snow, state government offices closed two days in a row.

CARL AZUZ: Another effect of all this winter weather is that many U.S. schools have been closed. Part of the reason's because of ice and snow, but part of it is because it's dangerous for students to wait at bus stops in the extreme cold.