Imbolc is a Celtic holiday that is also called cross-quarter day. It is celebrated on February 1st or 2nd and falls halfway between the Winter and Spring equinoxes. Imbolc represented a time of the year when food was getting scarce and people were ready to banish Winter and start getting crops in the ground. Since this holiday was agriculture-oriented, it is related to foretelling the weather, which is the partly the origin of Groundhog Day. It was called Brigid's Day on the old pagan calendar, which was adopted as St. Brigid's or Candlemas Day by the later christians.
Naturally if you want to banish Winter, you send the chill away by lighting a fire. You can also light candles in your home to light up the dark Winter night. Imbolc also was celebrated because as the Spring equinox approached, the days started getting longer, which melted the snow and warmed the ground for planting seeds. The candles are also representative of the sun staying up longer and getting warmer as Winter draws to a close.
At this time, animals started giving milk in anticipation of bearing their young in the Spring. Traditional foods to celebrate Imbolc are milk or dairy products like cheeses, and also seed-based items like whole grains. I don't know if we will have a bonfire or what, but we have wood stacked and ready, the seed catalogs are already being reviewed, and we are ready to head towards the warmth of Spring.
Happy Imbolc all!