You can go outside once your day length is about 13 hours(late April), as long as the plants were switched to 13/11 at about three weeks old. This way, when the plant goes outdoors, it won't experience a reduced day length, triggering flowering.
(Grown from seed, most strains become sexually mature at about six weeks, and will respond to a shortening day length and begin to flower. Another guideline is when the sixth true pair of leaves arrives. Many strains will begin blooming at that point, IF the day length is diminishing or the day is 12 hours or shorter.)
A friend took several plants outdoors last May(after I'd explained about photoperiods), from an 18/6 schedule into the outdoors which was at 14 hours of sunshine. The plants all began to bloom, and only reverted to veg, a few weeks later. This slows vegging but his outdoor girls still averaged over a Kg each, last fall.
OR
You can do what I do. Put them out in pots after your last frost date, and get a small Spring crop. In my area, I must harvest Spring buds by April 15th to avoid all the buds beginning to reveg, losing potency. Leave about 1/3 of the vegetation on these plants, leaving plenty of sites to reveg from.
Hope this helps!