May 1st or when the threat of frost is gone. You technically could now, however depends what your planting as well, Auto, or regular, if its regular I see that in your neck of the woods right now the sunrise is at 6:17am and sun set is at 19:36. So now that we have found out when the sun rises and sets we know how many hours of sun we are getting. 19:37 - 6:17 = 13:19 hours of sun, you may plant outside as soon as the average daily temps are at least in the 60's, and when I consult the internet again about the weather where you live I see that May is a good time to start planting.
This my friend is not only an answer but it is also a feeding of information by spoon to a Dude that refers to himself on the internet as a Dutch Master, which is laughable.
GFYS