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a period of unusually cold weather

a wave of unusually cold weather

a period of unusually cold weather

In the terminology of the United States Weather Bureau, an unusual fall in temperature, to or below the freezing point, exceeding 16¡ in twenty-four hours or 20¡ in thirty-six hours, independent of the diurnal range.

In the terminology of the United States Weather Bureau, an unusual fall in temperature, to or below the freezing point, exceeding 16¡ in twenty-four hours or 20¡ in thirty-six hours, independent of the diurnal range.