If the weather would only decide to be fall, already, we'd have issues with them too ... both in the kitchen and in our 2nd floor bathroom (which is actually 3 stories up because of the way the lot slopes - plainly ants do not suffer from acrophobia).
The poison bait stuff that they carry back to the nest so that it kills the whole colony is pretty effective. And in the meantime, if you find out the spot through which they're entering your space, you can draw a "fence" of cinnamon oil (any store with a good baking section, or a speciality shop for baking/candy making) around it, and they won't be able to cross it (remember to make your circle continue onto vertical surfaces, if necessary). It mucks up their scent-following receptors. And it's non-toxic (hmmm ... to humans, anyway, and your cat probably won't like it) in the quantities you'd use.