Answer: Ideally, you should wait until all danger of frost is past before planting tomatoes outdoors. Even if they survive a cold spell, their growth may be set back, so it's best to wait. You can set them out a week or two earlier if you have row covers or "wall-o-waters" in place to hold in the day's heat through the night.
According to my map, your last spring frost occurs sometime around April 20, so you should be OK, though be prepared to cover them if a frost threatens. However, if a gardening neighbor told you it was too early, I'd follow their advice. Perhaps you are in a cold pocket that is susceptible to later frosts than your surrounding area.
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