I agree, you most likely have Thamnophis sirtalis parietalis. they're probably one of the northernmost species of snakes in north america, and they have a very interesting life history which involves mass hibernation and a mass exodus/breeding in the springtime. try looking them up on the internet sometime. they also go by the common name red-sided garter snake, but they're not really that red if you ask me.
:Most likely what you have is a red-sided garter(T.s.parietalis). Despite the name "red-sided", most Canadian specimens are just black with the yellow stripes, unlike the parietalis of the midwestern lower 48's.