I think that's a problem with the font, actually - it's supposed to be monospace, but the diagonal arrows (e.g. ↗) are about 1.5 times the width. I have the same problem.
(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?)
Thanks for confirming. Can you share the font/fontname you are using? I would like to install it on my PC as well...
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.
Looks like certain assumptions about max length of weather numbers causes unnecessary additional padding resulting in misaligned borders.
http://imgur.com/vyupGUN