Our rule of thumb in my area is not to plant anything until May 1, because we ALWAYS have a warm April followed by a late frost. More experienced gardeners laugh at all the people flooding Lowes in April!
So last year I started planting on May 2, just for it to all be destroyed on May 15. I don't remember EVER having one that late in the year, either :-O
I just read that the local weather is calling for frost Friday morning... better stock up on trash bags so I can cover all of my perennials!
https://www.gowilkes.com/weather/