Seedlings · outdoor acclimation
Can I put my seedlings outside today?
Indoor seedlings need gradual exposure to sun, wind and outdoor temperature. Choose your plant type and hardening progress; we’ll combine that with your local forecast to tell you how to proceed without rushing.
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Why this decision matters
Two weeks of progressively longer sheltered outings is a useful pattern, not a guarantee. The NWS grid temperature cannot measure conditions inside a pot or against a sunny wall.
Why hardening off matters
Seedlings raised under lights or indoors have never experienced outdoor ultraviolet radiation, gusty winds and day-to-night temperature changes. Abruptly putting them into full sunlight can scorch leaves and cause wilt or death.
University of Minnesota Extension describes a roughly two-week acclimation: start with a few hours in protected shade, add more time and sun gradually, and bring plants indoors as temperatures drop. A ventilated cold frame can help but still requires attention during cold and sunny periods.
Frost protection comes before the schedule
Warm-season transplants such as tomatoes, peppers and basil are vulnerable to chilling and freezing. Even an established hardening routine does not make them frost-hardy. Cool-season seedlings have different tolerances. If the NWS source is missing or outdated, this engine refuses to label outdoor nights safe.
Horticultural guidance: University of Minnesota Extension — Starting seeds indoors / Hardening off seedlings.
Location evidence uses National Weather Service hourly forecasts, NOAA climate normals and USDA plant hardiness. The forecast is not a measured leaf or soil temperature; climate averages are not predictions.