I can tell you when I start mine and when I move them outside. I'm in "mid-Michigan" and my plants are in a greenhouse every summer. I start my summer crop indoors the last week of March. I move them outside to my greenhouse around the 15th of May. This is a variable that changes based on 15-30 day weather forecasts for my area. I don't like putting my plants out in my (unheated) greenhouse when the night time temperatures are consistently still hitting the 30's- lower 40's. I would also pay a lot more attention to the weather if you're planting them directly outdoors. Most people in my area start their outdoor vegetables like tomatoes and peppers around Memorial Day. By then, you'll be safe putting young plants outdoors.
More important is your choice of strains. Many won't finish before the fall weather consistently hits dew point. This is much more important to pay attention to than your average annual frost date. Once your night time begins to hit dew point regularly, the chance of mold/mildew/bud rot rises significantly. Daily trips outside with a battery powered leaf blower to dry your plants off is an "SOP" in my neck of the woods.
