If your fields sit in a valley bottom, plan against the conservative end of your county's frost-date table.
Frost Dates & Planting Timing
Why are valley bottoms more frost-prone than nearby hilltops?
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.
More from Frost Dates & Planting Timing
- When is the last frost date in my area?
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- How do I use frost probability tables for planting decisions?
- What is a killing frost vs. a light frost?
- Can I plant earlier using row cover?
- How do I protect plants from a late spring frost?
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