The Great Snow was really a series of four storms that struck in quick succession in late February and early March of 1717. No one is quite sure how widespread the effects were, as record-keeping was spotty in colonial New England. Heavy snow was recorded as far away as Philadelphia, but Boston got hit the hardest.
That winter had already been a snowy one, with reports of five feet (1.5 m) of snow already on the ground when the Great Snow began. Three or four more feet (91.4 or 122 cm) were added to that total, with drifts reportedly reaching 25 feet (7.6 m), burying entire houses or forcing people to exit from second story windows [source: NSIDC].
Such a massive snowfall would've hit hard in any era. But at a time when one could travel only by horseback or on foot, when no method of snow removal beyond a shovel and a strong back was available, and when many small communities struggled in ordinary winter conditions, the Great Snow hit especially hard. Roads were blocked for a week or more, and travel between New York City and Boston was impossible. In fact, there wasn't really anything that could be done about the roads -- except to wait for warmer weather to melt the snow.