On February 2, 1887, Groundhog Day, featuring a rodent meteorologist, is celebrated for the first time at Gobbler’s Knob in Punxsutawney, Pennsylvania. According to tradition, if a groundhog comes out of its hole on this day and sees its shadow, it gets scared and runs back into its burrow, predicting six more weeks of winter weather; no shadow means an early spring.

Groundhog Day has its roots in the ancient Christian tradition of Candlemas, when clergy would bless and distribute candles needed for winter. The candles represented how long and cold the winter would be. Germans expanded on this concept by selecting an animal–the hedgehog–as a means of predicting weather. Once they came to America, German settlers in Pennsylvania continued the tradition, although they switched from hedgehogs to groundhogs, which were plentiful in the Keystone State.

Groundhogs, also called woodchucks and whose scientific name is Marmota monax, typically weigh 12 to 15 pounds and live six to eight years. They eat vegetables and fruits, whistle when they’re frightened or looking for a mate (they’re sometimes called whistle pigs) and can climb trees and swim.

READ MORE: Beyond Punxsutawney: Meet the Other Groundhogs

They go into hibernation in the late fall; during this time, their body temperatures drop significantly, their heartbeats slow from 80 to five beats per minute and they can lose 30 percent of their body fat. In February, male groundhogs emerge from their burrows to look for a mate (not to predict the weather) before going underground again. They come out of hibernation for good in March.

In 1887, a newspaper editor belonging to a group of groundhog hunters from Punxsutawney called the Punxsutawney Groundhog Club declared that Phil, the Punxsutawney groundhog, was America’s only true weather-forecasting groundhog. The line of groundhogs that have since been known as Phil might be America’s most famous groundhogs, but other towns across North America now have their own weather-predicting rodents, from Birmingham Bill to Staten Island Chuck to Shubenacadie Sam in Canada.

In 1993, the movie Groundhog Day starring Bill Murray popularized the usage of “groundhog day” to mean something that is repeated over and over. Today, tens of thousands of people converge on Gobbler’s Knob in Punxsutawney each February 2 to witness Phil’s prediction. The Punxsutawney Groundhog Club hosts a three-day celebration featuring entertainment and activities.

READ MORE: Groundhog Day History and Facts