when is official start of winter
Meteorological winter starts on 1st December. Winter solstice is 21st/22nd December when the sun is at it's weakest. However, due to seasonal lag this is still in the first third of winter generally (look at seasonal lag on wikipedia) and is not the middle of winter at all for that reason. Calendar winter also begins on the solstice. However, overall it starts to feel like winter in late November.
Winter solstice is the day with the fewest hours of sunlight during the whole year. In the Northern Hemisphere, it always occurs around December 21 or 22. (In the Southern Hemisphere, it is around June 20 or 21.) Find out the changing day length in your neck of the woods with our personalized Sunrise/set tool.