In 2 weeks my tubers went from more or less nothing to sprouts ~3" tall. Depending on how deep you've planted them, its not unrealistic that they still haven't broken the surface.

I'll vote for you being too impatient.

Do remember that any air frost may very well kill any growth above ground. I too am in Ontario and would not be comfortable putting out dahlias that are above the surface until the last week of May, at the earliest, unless I had a way to protect them from the frost. Might want to stick to your bring them back in at night for a while longer.

I remember a few years ago we had Zero C on the May 24th weekend.

Cheers,
Russ

Thanks, I will continue to bring them into the garage at night.