Rex Marsh, 71, can recall winters so cold no one in northern Vermont ever thought of tapping a sugar maple before town meeting day on the first Tuesday of March.
Yet for the last two years, the Marshes have tapped their maples in January, the earliest they can recall in five generations of sugar making, The Los Angeles Times reported.
In response to rising global temperatures, spring comes as much as 13 days earlier in many parts of North America -- and 15 days earlier in Europe -- than it did 30 years ago, scientists say.
Spring and winter are becoming milder, the National Climatic Data Center reports. From 1950 to 1993, the coldest winter temperatures rose by 5 degrees, and the warmest spring temperatures rose 2.5 degrees.
Searching for reliable clues, scientists have turned to people such as Marsh - who for generations have kept a precise weather eye on the seasons.