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Regional Calendars, Climate & DataCreating a County-Level Crop Calendar
A county is a good unit for a crop calendar: small enough to share a climate, large enough to have data. Here is how to put one together.
Key points
- County-level calendars combine freeze data, soils, extension guidance and insurance dates.
- Use separate zones where a county has large elevation or soil differences.
- Review the draft with extension staff and experienced local growers.
- Update annually and label risk levels and data sources.
- Share your draft with extension and local growers, and update it every year.
Why build at the county level?
Extension offices are organized by county, insurance and farm program data is often kept by county, and some freeze tools report by county. The Midwestern Regional Climate Center freeze date tool, for example, gives earliest, early, average, late and latest freeze dates by county for the north-central and northeastern states.
That makes county a practical way to bring data, advice and local knowledge together.
County lines are an administrative choice, not a climate boundary, so check whether neighboring counties share your conditions. Sometimes a calendar for a group of counties fits better than one for a single county.
What data should you gather?
Frost and freeze probabilities for your county or for stations within it, growing season length, and climate normals for rainfall and temperature. Add soil survey information from USDA NRCS, since soil type affects warming and drainage. Collect the extension planting guide for the county or state, and the RMA insurance dates for each crop.
If your county has large changes in elevation or soil, collect data for two or three representative stations or zones.
Soil survey information from USDA NRCS can tell you about drainage and water holding capacity, which help explain why one part of the county plants earlier than another.
- Frost probabilities at several thresholds
- Climate normals for temperature and rainfall
- NRCS soil information
- Extension planting guide
- Insurance planting dates
How do you organize the calendar?
Use a grid with crops down the side and weeks or months across the top. Mark frost anchors at your chosen risk level, planting windows, key growth stages and harvest windows. Add a column for risk notes, such as late frost sensitivity at bloom or the chance of wet field conditions.
Keep a separate version for each zone within the county if conditions differ substantially.
Keep a notes column for local lessons, such as which fields flood in spring or which crops have done poorly in local conditions. Ask the extension office whether similar calendars already exist for nearby counties so you do not repeat work.
How do you check it against local knowledge?
Take the draft to your county extension office and to experienced growers. Ask where it differs from what they do and why. Often the difference is a risk level or a soil type, and the conversation will teach you more than the data does.
Extension staff may also know of local trial results and recent weather patterns that are not in published tables.
Include a short list of local contacts, such as the extension office, the Farm Service Agency office and the NRCS field office, so the calendar points to help as well as dates.
How do you keep it current?
Update it each year with actual planting dates, weather events and results. Revisit the data sources when NOAA releases new normals, which happens every ten years. Note any local changes, such as new varieties or new drainage, that affect timing.
A calendar that records a decade of local experience becomes a valuable resource for the whole county.
Update the calendar after any major weather event, such as a late freeze or a flood year, and record what it meant for each crop.
What should you avoid?
Do not present the calendar as official guidance or as a substitute for extension advice. Do not average over zones that differ greatly. Do not state dates without noting the risk level and the data behind them.
Make clear that the calendar is a planning aid, that dates are not guarantees, and that growers should check the forecast and soil conditions each year. Offer to share your results with the office, which can help improve guidance for everyone.
How do you share it with other growers?
A calendar that others use gets corrected faster. Offer a draft to neighbors, a grower association or a local extension meeting, and invite comments on dates, risks and crops that are missing.
State clearly who wrote it, what data it draws on and when it was last updated. Make it plain that it is a planning aid and that each grower should check forecasts, soil conditions and current extension guidance.
Sources and further reading
Last reviewed: November 2026. Educational information, ranges only. Confirm timing with your county extension office.