cipollini onion seedlings

Planted my cipollini onion seeds indoors and they have come up. My question is, is it too early to plant them in the ground? Our average last frost is the end of April. Do they tolerate mild frost?

theres a lot of different varieties, but many onions can be grown through the winter and are often planted in early fall.
you can totally plant them up now, they do ok in cool and cold weather.
when it gets hot they tend to flower, so its good to start them early and get them big enough before that happens. cause then they put their energy into flowering and not growing bigger bulbs.