from Wikipedia:

Imbolc is one of the four principal festivals of the Irish calendar, celebrated either at the beginning of February or at the first local signs of Spring. Originally dedicated to the goddess Brighid, in the Christian period it was adopted as St Brigid's Day. In Scotland the festival is also known as Latha Fhèill Brìghde, in Ireland as Lá Fhéile Bríde, and in Wales as Gwyl Ffraed.

While in the Northern Hemisphere Imbolc is conventionally celebrated on 1 February, in the Southern hemisphere it is sometimes celebrated on the calendar date, but those who see it primarily as a celebration of spring may move it to 1 August.

Imbolc is traditionally a time of weather prognostication, and the old tradition of watching to see if serpents or badgers came from their winter dens is perhaps a precursor to Groundhog Day.

Thig an nathair as an toll
La donn Bride,
Ged robh tri traighean dh’ an
Air leachd an lair.

"The serpent will come from the hole
On the brown Day of Bride,
Though there should be three feet of snow
On the flat surface of the ground." [1]

Fire and purification is considered by many to be an important aspect of this festival. Brigid (also known as Brighid, Bríde, Brigit, Brìd) is the Goddess of poetry, healing and smithcraft. As both goddess and saint she is also associated with holy wells, sacred flames, and healing. To some, the lighting of candles and fires represents the return of warmth and the increasing power of the Sun over the coming months. [2]