The winter of 1999-2000 was the warmest winter in the U.S. since the government began keeping records 105 years ago, marking the third year in a row of record warm winters, said the National Oceanic and Atmospheric Administration. From December 1999 through February 2000, every state in the contiguous U.S. was warmer than its long-term average, and in many places from the Northern Plains to New England, the first snowfall and first freeze came later than ever. Since 1980, more than two-thirds of U.S. winters have been warmer than the long-term national average. NOAA attributes the warming in part to human-caused global warming. Milder winters are consistent with a global warming trend that most scientists believe is at least partially caused by humans.