Weight of snow isn't nearly the issue that many folks think it is. Four feet of snow weighs about what 4-8 inches of water would weigh -- not all that much. The deck is pretty-well built. As for what is on the rooftop -- well, again, roof trusses are engineered for local conditions, so I don't worry when there's only four or five feet of snow up top -- and that doesn't happen very often.
As for the old wive's tale about the snow needing shoveling when the temperatures get up to where the snow would melt -- wait a minute -- the snow is turning to water but the total amount of weight remains the same. Yes -- a partial meltdown followed by more feet of snow might be a bother -- but we don't usually lose much of the snowfall 'til it's all about to go for spring -- usually by May.