Tonight temperatures in our locality are dropping to 30F (-1C) in the ealy next morning. The foliage on my 'under 1 year old' plants is green. Should they be brought inside garage even if the low temperature is to last only for a couple of hours before sunrise?

They can probably take it, but better safe than sorry!  If you have a lot of them, maybe cover with a blanket?

When in doubt....bring them in.  That is what I would do.  cheers!

The question is what are you planning to do with them in winter? if you want them to go dormant than not a big problem, but if you plan to keep them indoors then don't let them get the frost. 

Absolutely. Happened last year around this time at my place and all tender limbs & leaves were fried. Some new starts never recover.

Ottawa (Kanata to Orléans)
FROST WARNING IN EFFECT

Dieseler <~~~ late to the party and enjoying a codeine high !
Hey its my tooth killing me i have excuse and need it pulled asap, im loseing my teeth.

Anyways back on track, Akram getting patchy frost tonight as well last night it dipped into the 30s im sure. I took several plants into garage including my sick Ischia and will do so once again tonight.

My reasoning is there still is some Autumn weather left with highs in 60s and i try to make there season as long as possible, sooner than later when cold weather is here for the most part which will be any week now i will give them there dormant treatment and into garage for good.

I thought to put the pots on the ground and cover with a tarp so ground heat will help moderate the temperature. I just covered it and don't mind if the wind blows it off because then the cold air will not settle down either.