Aleks sends along this dynamic graphic from Mike Bostock:
I’m not so happy with the arrangement of years by decade—the lineup of all years ending in 0, or 1, or 2, etc., seems a bit of a distraction—but in many ways the display is impressive. And, as often is the case with such graphs, once it’s out there, other people can do similar things and make their own improvements.
I don’t like it. 38 maps x 12 months is hard to interpret. Not a summary.
I would prefer 4 maps, one for each season, averaged over all years or by decade.
P.S. The averaging might mess with the definition of drought which presumably is a deviation from some average.