Q.Frost Dates & Planting Timing
Why are valley bottoms more frost-prone than nearby hilltops?
A.
Cold air is denser than warm air. On clear, calm nights, cold air sinks down slopes and pools in valley bottoms — creating a temperature inversion where the valley floor can be 5-10°F colder than slopes 100-200 feet above. Valley orchards frost earlier in fall and later in spring than ridge-top orchards.
If your fields sit in a valley bottom, plan against the conservative end of your county's frost-date table.