During the past 30 years, there has been an increase in the length of the frost-free season over the contiguous United States and Alaska, relative to the 1979–2017 average. The bars on the graph show the difference between the number of frost-free days in each year and the average number of frost-free days from 1979 to 2017.
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Last modified:
17 September 2019 - 12:53pm