A frost date is a climate estimate, not a deadline.
Seed-starting advice often tells gardeners to work backwards from a “last frost date,” but many people do not know what that date means for their own area. This tool looks at ten complete historical years and finds the threshold dates for each year before taking a median.
Using several years avoids pretending one unusually warm or cold season is normal. It still cannot resolve the exact microclimate of a back garden, so use the result as a planning anchor and then let short-range frost forecasts refine the decision as planting time approaches.