"When Groundhog Day arrives Saturday, don't waste much time expecting to see your local groundhog. It's too early. Normal emergence in the Washington area is late February or early March — but a steadily warming world might change that."
"In some parts of the country, groundhogs and other marmots have been leaving their burrows earlier than usual. By 2010, groundhogs in Maine were emerging about 17 days sooner than in 1998, according to marmot expert Kenneth Armitage, a professor emeritus of behavioral ecology at the University of Kansas.
When a groundhog, also known as a woodchuck, pops its head out of his burrow, he's focused on the temperature of the air, not the angle of his shadow. If the marmot senses it's too cold to start the season, he will retreat to his hibernaculum and slip back into torpor."