Mr Abbott kicked off his attack in the Hunter Valley, a coal-mining region of New South Wales, where he branded the tax a threat to coal's future.

ECONOMIST: The prime minister stakes her future on a divisive scheme

In the Hunter Valley 150 km (93 miles) north of Sydney, mid-January is harvest time in what has long been recognized as one of Australia's premium wine growing areas.

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For the Hunter Valley's winemakers, timing is everything.

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After several days of 40-plus temperatures this week and a forecast for temperatures in the Hunter Valley to reach 42 degrees Celsius (107.6 degrees Fahrenheit) again on Saturday, plus the possibility of thunderstorms, the winemakers face some tough decisions.

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