Question 1

How is soil temperature estimated?

Accepted Answer

Soil temperature at the 2-inch depth lags air temperature by about 3-5 days and smooths out daily swings. The standard extension-service approximation is a 7-day rolling mean of daily average air temperature. That's what this tool uses. In practice, sunny beds with dark mulch run 3-5°F warmer than the estimate, and shaded or heavily mulched beds run a few degrees cooler. For more accuracy, stick a soil thermometer in the bed for three mornings and average the readings.

Question 2

Why does the tool wait on tender crops even when it's above freezing?

Accepted Answer

Tender crops like tomatoes and basil don't actually die at 33°F. They stop growing below 50°F and suffer cold damage that takes weeks to recover from. A string of 35-40°F nights early in the season will produce stunted plants that underperform plants transplanted two weeks later into warm soil. The soil-temperature check is what forces a yellow or red even when there's no frost in the forecast.

Question 3

Is the 14-day forecast reliable out to day 14?

Accepted Answer

Days 1-7 are usually within 2-4°F of reality. Days 8-14 get progressively less accurate and should be treated as guidance, not commitment. The tool weights the first 7 days for the freeze check and soil estimate, so day-14 noise has minimal impact. If you want to be ultra-safe on a planting day, re-check 48 hours before you were planning to sow.

Question 4

Should I trust this more than the Farmers' Almanac last frost date?

Accepted Answer

For the 'should I plant this weekend' question, yes. The Almanac date is the 50th-percentile last frost, averaged over a large region. This tool uses YOUR ZIP's actual 14-day weather. When they disagree, the live forecast wins. For long-range planning (when to start seeds in February for a May transplant), use the seed start calendar tool instead, since it's based on your ZIP's actual historical last-frost date.

Can I Plant Today?

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