Q.Frost Dates & Planting Timing
What is the difference between a hardiness zone and a frost date?
A.
USDA hardiness zones measure average annual minimum winter temperature — useful for predicting whether perennials survive winter. Frost dates measure when last spring and first fall frosts actually occur — useful for planning annual crop planting and harvest. Zones tell you about peach trees; frost dates tell you about tomatoes.
A USDA Zone 7 designation means average annual minimum is 0 to 10°F. It says nothing about when the last frost typically occurs in spring or how variable that date is. Two locations in the same zone can have last-frost dates 2-3 weeks apart. Frost-date pages give the actual probability distribution for your county.