"Blizzard" is a term that gets bandied about rather casually. I think the National Weather Service has criteria for a blizzard (just as they do to differentiate between a "tropical storm" and a "hurricane"). I believe it has to do with a combination of both wind speed and how much snow falls in a given period, probably an hour. But I don't recall exactly what the parameters are. So in theory you can have a very heavy snowfall that isn't technically a blizzard because the wind isn't strong enough at the time the snow falls.
I wouldn't mind being in Boston right now. Sounds like fun. ...
In the United States, the National Weather Service defines a blizzard as sustained 35 mph (56 km/h) winds which leads to blowing snow and causes visibilities of ¼ mile or less, lasting for at least 3 hours. Temperature is not taken into consideration when issuing a blizzard warning, but the nature of these storms are such that cold air is often present when the other criteria are met.
Blizzards are formed when a high pressure system, also known as a ridge, interacts with a low pressure system; this results in the advection of air from the high pressure zone into the low pressure area.
Note that this latter characteristic (the pressure systems) is the same thing that causes a nor'easter, but nor'easter, as I said earlier, can be a rain or snowstorm. That's why I suggested that a blizzard is a particular type of nor'easter, particularly here in the northeast!
L