When fog forms below 0C, its super-cooled water droplets remain liquid, even though the temperature is below freezing.

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These systems are not only important in the winter months, but also in the summer months, because at higher altitudes, the temperature is well below freezing year-round.

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"In wintertime, the cliff surface gets so cold that its temperature falls below the freezing point of CO2, which at low pressure goes directly to solid, " said Dr Musselwhite.

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The outdoor temperature had fallen below freezing, but Mr. Tamm was dressed in just a pair of shorts and a white floppy hat with the words "Sauna Boss" embroidered across the front.

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Skiles, 49, as well as rescuers, who acted quickly to minimize passengers' injuries in below-freezing temperature and frigid water.

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Inside the greenhouse, lines of bright sodium lights shine down on the growing tomato plants, and the temperature remains a constant, warm 23C -- even in the depths of winter when outside temperatures drop well below freezing.

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