According to the Free Dictionary:
1. Of, relating to, or limited by time: a temporal dimension; temporal and spatial boundaries.
2. Of or relating to the material world; worldly: the temporal possessions of the Church.
3. Lasting only for a time; not eternal; passing: our temporal existence.
4. Secular or lay; civil: lords temporal and spiritual.
5. Grammar Expressing time: a temporal adverb.
Definition #3 is almost identical to their definiton of "temporary":
Lasting, used, serving, or enjoyed for a limited time.
So, given that, I guess you could make the argument that this sign isn't wrong. It just sounds and looks funny as hell. It brings to my mind some scenario in which time does not pass within the walls of this liquor store. When they eventually open the doors to the public, all products with dates on them (a package of chips, for example) will appear to us to have passed their expiration dates, but the products themselves will still be as fresh as the day the owners shut the portals of their amazing time-traveling establishment. Maybe they plan to stay inside until sometime in our distant future. When they reopen they'll be able to sell antique bottles of booze at a substantial markup.
A more likely explanation is that this is yet another example of an all-too-common phenomenon: professional sign makers who don't know how to spell.
This is not the only problem with this joint:
No apostrophe for Spike and his Bottle Shop. Or do they sell spikes and bottles? Yet they got it right on another sign:
Why the inconsistency? Perhaps when Spike emerges from his TARDIS-store, the anti-apostrophe people will have finally achieved their goals and some member of the Apostrophe Patrol will have whited out that pesky punctuation mark for him.