The Winter Solstice arrives on December 22nd in the early morning hours for eastern Canada, and the evening of December 21st for the rest of the country.
This marks the beginning of astronomical winter, however, many parts of Canada have already experienced winter weather.
On this day, the Sun reaches its southernmost position over the northern hemisphere.
The Sun also rises and sets at the southernmost position in the sky. Since the path of the Sun is the lowest over the horizon, we have the shortest day of the year.
The good news is that the Sun starts its northward journey in the sky after the Winter Solstice, so the days get longer. Day and night will become more or less of equal length when the Vernal Equinox arrives on March 20th of 2012.