If you don't have a hoophouse/greenhouse, the general grandma's rule of thumb for avoiding frost is the first Sunday after Easter, which is April 11th, BUT the days are not long enough yet. I will wait until the first week of May for outdoor cannabis. It depends too on how well your garden is exposed to the sunlight. According to timeanddate.com, on May 1st in OKC there is about 13.8 hours of daylight. May 13th will be the first day with at least 14 hours daylight. If you plant too early in April, photoperiod plants will start to flower, but they will reveg before they finish. That's okay, they'll continue to grow through the season just fine. Any day when it's above 50F, I take my plants outside to get a few hours of direct sunlight, so they'll get hardened off to sunlight, but also get extra light after sunset. I'll plant in larger cloth pots outside after May 13, so I can move them under cover in case of hail. Then by the beginning of July (there's still hail risk after this but the worst has passed by then), I'll leave them in the ground to get big.