It's pretty cool, but it doesn't quite line up for me. Unicode characters (but ... "ASCII"?) are the prime culprit, but something also going on with the 'delimitting' header lines too - they're way off.
Looks like certain assumptions about max length of weather numbers causes unnecessary additional padding resulting in misaligned borders.
(Or maybe not "the" font, but fonts in general - perhaps it's trying to use one font, which doesn't have these arrows, so it falls back to a different one?)
Update: Looks like they fixed it now. I just re-visited the site after posting this comment and see that there are new monospace arrows rendering in a properly aligned manner.