In answer to your question, I assume that you mean when is it ok to transplant your plants outdoors?
Since MJ is responsive to the available lighting as to when it 'decides' to switch from veg to flower your choice of when to transfer it outdoors should be made with that in mind. I am at 40 deg. n. and this means mid May to June is the ideal time. For your area you should try and figure when 14 hrs of daylight occures in your latitude and use that as a guide. If you move them outdoors too early they will imediately go into flower mode. No real harm in this, but when the sunlight gets longer in late spring they will revert back to grow mode. This can cause several different problems and wastes valuable veg time on your plants. I know, I tried it when I first started growing. The resulting plants where shorter, and yeild wasn't as good as when I waited for the 'proper' time to plant.
There is no hard and fast rule for how big your plants should be when you do finally put them out, as long as you introduce them to sunlight gradually and as long as they have a good root structure they will be fine. I generally let them get about 16 inches or bigger befor I transplant them outside, but some grow them indoors until they get 3 or 4 feet.
