In a little more than 24 hours time (at 03h38 UTC, on 22 December 2010) the Sun will reach it’s southernmost point in our skies and begin moving back North. Or, to put it in a slightly less geocentric way, the Earth will pass through the point in it’s orbit where the south end of its polar axis will come closest to pointing at the Sun. This is called a Solstice. The December solstice marks the official beginning of Winter in the Northern Hemisphere, and Summer in the South.
Of course, foolish ordinary folk have been complaining about the heat for months now. They say “When will this summer end?”. But you and I know better: Astronomically speaking it hasn’t even begun!