Yes, they will still bloom :-)

Occasional bumps in temps will have no ill effect. And I doubt your overnight temps are in the 60's anyway and that tends to be more crucial than daytime temps. And because the pots are out of direct sunlight in a garage, the heating of the container soil is much less likely to occur and it is really warming soil (and light) that will start to stimulate unseasonal growth.

It would be highly unusual for you to continue indefinitely with such a mild winter in a zone 5 so I really don't think you need to be overly concerned. The temperatures should resume their normal range and as long as the pots are kept in the coolest location possible and with minimal light you should be good.