I think I'm a bit warmer earlier than you are. Being next to two bodies of water seems to make a difference, bringing me a microclimate. I can start planting in April, all the cool-loving plants. I've already harvested tons of lettuce, arugula, kale, and spinach. Soon, the Chinese cabbage will be ready to make kimchi. lol
Just think, you get to enjoy your peonies soon, and mine are almost done. I will miss them.
I bet the bodies of water do make a big difference. Enjoy those greens! People around here are harvesting them, too, but I didn't get around to planting any.
I believe it makes me a Zone 6b with the two lakes.