The frost dates in our workbook and packs belong to NOAA weather stations, not to towns. Choosing the right station is the biggest decision you make, and it takes about five minutes.
1. Start with distance, then check elevation
Look for the closest stations to your garden. Then compare elevation: the tables list it in feet for each station. As a rough rule, every few hundred feet of elevation can move freeze dates by days, and in mountain country by weeks. A station five miles away on a valley floor may be a worse match than one ten miles away at your elevation.
2. Consider the setting
Airport stations are typically on flat, open ground. Stations in towns and cities can be warmer than the countryside, and stations at the bottom of a valley can be colder because cold air pools there. Think about whether your yard is more like the station's setting than like the next one over.
3. Read the completeness flag
NOAA flags how complete each station's record is. In the tables:
- S (Standard) has 24 or more years of data.
- R (Representative) has 10 or more years, with gaps filled from neighbouring stations.
- P (Provisional) and E (Estimated from nearby stations) rest on less complete information.
When two stations are about equally close, prefer the one with a better flag.
4. Compare two or three
Pull up the two or three nearest stations. If their dates are within a few days of each other, you can be comfortable. If they differ a lot, ask why (elevation, coast, valley) and choose the one that resembles your yard.
5. Use a local check
Your own notes are the best correction. Many gardeners record the last spring freeze and first fall freeze in their yard each year, and after a few seasons they know how far their yard runs from the station. Our Garden Journal has a freeze-event log for exactly that.
Where to look
- In the workbook, choose your state and search part of a station name; the list shows the matches with elevation.
- In a regional pack, use the printed station tables for a spread-out selection and the CSV for every usable station in the region.
- NOAA's own site publishes the same normals; our products cite the dataset (doi:10.25921/4ek7-fk11).
The dates are historical statistics, not a forecast.
Want the dates for your own station? See the Garden Calendars workbook and regional packs, or the free sample PDF. Next guide: Why frost dates are not forecasts.
Please note. Historical 1991-2020 averages from NOAA; actual frost dates vary year to year; not a forecast or a guarantee; not agricultural advice. Planting windows are generic offsets from historical dates; follow your seed packet, your local extension office and the current weather forecast. This product is AI-assisted, so errors are still possible; please report them to gb1@mail.grokbot.com.
Source: Palecki, M., Durre, I., Applequist, S., Arguez, A., Lawrimore, J. (2021). U.S. Climate Normals 2020: U.S. Annual/Seasonal Climate Normals (1991-2020), version 1.0.1. NOAA National Centers for Environmental Information. doi:10.25921/4ek7-fk11. Quietcog is independent and is not affiliated with, endorsed by or sponsored by NOAA or the National Weather Service. Quietcog processed the station files; any processing errors are ours.
Support: gb1@mail.grokbot.com.