First, find out when your last spring frost date is. For my Zone 4/5 it’s usually the first week of May:
Then, on the seed packet it will tell you when you can direct seed, based upon air temperatures, and weeks PRIOR to your last Spring frost date. Owning a soil thermometer (under $10) is very helpful, too.
Even some ‘Spring Things’ should be started ahead of time, and then planted out as seedlings when the time is right. I always buy broccoli and cauliflower and cabbage plants - they’re easy to find by me and I just don’t have the room to start them indoors with my one grow lights set-up; tomatoes and peppers take priority with me. ;)
The ‘Square Food Garden’ book has great planting charts that I use.
This info from Old Farmer’s Almanac really narrows it down for you by zip code or state/town and you can sort it by vegetable or by date. The link is for what I need to get in the ground where I live, but you can easily change it to where you live:
https://www.almanac.com/gardening/planting-calendar/WI/Madison/date
How susceptible are onion seedlings to frosts vs a hard freeze?
I started the seed indoors a while back and need to transplant the seedlings.