Certified GKH Gardening Expert
While caladium bulbs require warm soil temps in order to sprout, this does not seem to be a problem for your location. On average, bulbs sprout within a week or two if they have been stored for any period of time, as dormancy is a natural part of their life cycle. The lesser storage time, the longer they take to sprout.
These articles will help with growing info: https://www.gardeningknowhow.com/ornamental/bulbs/caladium/caladium-plant-care.htm