This graph shows the extremes in one-day precipitation in a given month relative to the amount of precip in that month for the Northeastern US. So, if the green bar is at 30%, that means that that 30% of month’s precip fell in one event. The way this is computed is a little complicated because it is hard to define an “event” in time and space in relation to the time and space coordinates (as it were) we normally use. Check the source of the graph for a more detailed explanation. The point of this graph is that the opposite is true from what many expect: It isn’t the case that the snow was deeper back when you were a kid. It’s deeper now! (Check out this blog post for an explanation for why you may have misremembered your childhood.) There are a number of contributing factors to a pattern like this, with increasing extreme events, but the best way to think of this may be as an increase in the bimodality of the water cycle. Dry events are dryer (you may have noticed widespread drought) and wet events are wetter (as shown in this graph).