When should you plant tomatoes outside in Connecticut?
Short answer: Wait until local frost danger has passed and the soil is warm enough for tomatoes. UConn notes that Connecticut's average last frost varies by location and year, and recommends transplanting developed seedlings when soil is about 65°F and daytime air temperatures average 55–60°F. Chilling can injure many tomatoes below 50°F.
How to decide
Check your actual site
A sheltered coastal yard and a cold inland hollow do not share an exact safe planting date. Check recent conditions and the short-term forecast before setting seedlings out.
Inspect soil and seedlings
UConn recommends starting tomato seedlings indoors six to eight weeks before transplanting. Well-developed transplants are more reliable than rushing small plants into cold ground.
Choose the next action
If nights remain chilly or soil is still cold, keep seedlings protected and reassess. If conditions are suitable, transplant into a sunny, airy site and plan for support and consistent watering.
Important: USDA hardiness zones describe winter low temperatures, not a guaranteed spring frost-free planting date. Do not treat any ZIP-derived planning group as a measured site forecast.