You should take into account humidity, seeing as the best humidity level at say 80ºF or even 70ºF is <i>very</i> much more pleasant than the worst.<p>Also, IMO your minimum temperature criterion is probably a mistake. Nobody cares that it's a little chilly at 4am, and meanwhile you're selecting for more humid climates (because those have less diurnal variation).<p>If you wanted to make the selection criteria user-adjustable, though, I'd be really interested to see the results. (Also, nice job on the visualization, discretizing every grid square to a town is particularly cute.)