Late April or early May is traditionally the best time when you should be planting your garden. If you’re planting seeds, then sometimes you can even move that up a week or two to mid April, to ensure they’re in the ground and getting a good amount of water heading into May.
The real thing you want to look out for, especially during those cooler days toward the middle or end of April, are the off days when you wake up and see frost on the grass. This alone is enough to wipe out the early stages of your garden.
If you’re planting saplings – like tomato plants, basil, squash, etc. – then waiting even until that first week of May should be fine.