Here is a link that has the dates for the average last frost for your area:
[url]https://www.omafra.gov.on.ca/english/crops/facts/climzoneveg.htm[/url]
May 15th for us! But after gardening here a few years I wait until June for anything delicate (then again, my garden is REALLY exposed to the elements)
Vanessa raising organic vegetables, livestock, wildflowers, and family in zone 5A.
It is hard for me to imagine waiting to plant frost tolerant plants until June!
My growing season begins in February with cold weather stuff and warm weather stuff in March/April. By June, it is already 32°C daily and some plants begin to struggle in the heat.