The tubers wake up when the soil warms up. The soil temperature should be at least 55F for planting. Most Dahlia sellers have extensive instructions on growing--do a search for Dahlia care--there is lots available.

Thank you! I have researched but I haven't found much info about when I should put them outside in the containers. They aren't being moved to the ground. Do I water only once I see growth come up? thanks again

At my end of the foothills, nights are low 40s for the next week although the next few day times should be sunny and warm. If the soil in the pot is damp and cold, dahlias rot. If you want them earlier, you could water and set the pots in the sun AND bring them back in at night (it's too cold for them outside at night now). I'd prefer the nights stay more in the 50s for your pots to be outside - they cool off faster in pots than in the ground. If your soil in the garage pots is bone dry, you could have dead dried out tubers. They do need moisture in the soil to grow well - don't wait for signs of growth before watering the pots - go by temperatures and put a bit of water on the pots if they are bone dry (don't soak).