Stephan 2 Nw
frost dates.
A source-backed view of historical freeze risk at this weather station. Use it to understand the season, not as a promise about your garden or this year’s weather.
Seasonal freeze referenceOne date never tells
the whole season.
1991–2020 station normals
32°F minimum-temperature threshold
Last spring freeze
Among cold seasons with a freeze: probability of the last occurrence on this date or later.
The 10% date is later in spring than the median: a more cautious historical reference, still not a guarantee.
First fall freeze
Among cold seasons with a freeze: probability of the first occurrence on this date or earlier.
The 10% date is earlier in fall than the median: a more cautious harvest-planning reference.
These percentages are conditional on a cold season containing a 32°F freeze; they are not probabilities across all years. They describe historical climate, not this season’s forecast. The spring and fall probability directions are intentionally different. A garden can be warmer or colder than the reference station.
Try a harvest scenario.
If a historical freeze reference fits your crop and regional guidance, you can choose it as a calculator target. This action does not turn the date into a recommended harvest deadline.
Choose a planning year.
Percentiles are conditional on a cold season with a freeze. Some crops tolerate freezing; others need warmth well before it. Check crop and local guidance first.
The reference
behind the numbers.
- Official station name
- STEPHAN 2 NW, SD US
- NOAA station ID
- USC00397992
- Coordinates
- 44.2661, -99.4431
- Station elevation
- 550.2 m / 1805 ft
- Normal period
- 1991–2020
- Source retrieved
- 2026-10-02
- Source modified
- Tue, 27 Jun 2023 15:16:19 GMT
A baseline.
Not a forecast.
Weather stations measure a particular location. Differences in elevation, exposure, nearby water, terrain and urban heat can change conditions in an individual garden.
- 32°F is the station air-temperature threshold; visible frost on leaves can differ.
- Median dates still leave substantial historical freeze risk.
- Historical normals summarize 1991–2020, not current weather.
- Crop suitability requires regional horticultural guidance, soil warmth, cultivar and day length.
How strong is this reference?
| Source variable | Historical date | Years | NOAA completeness |
|---|---|---|---|
| Last spring freeze · 10% | May 24 | 17 | R · Representative |
| Last spring freeze · 30% | May 16 | 17 | R · Representative |
| Last spring freeze · 50% | May 10 | 17 | R · Representative |
| First fall freeze · 10% | Sep 16 | 17 | R · Representative |
| First fall freeze · 30% | Sep 24 | 17 | R · Representative |
| First fall freeze · 50% | Sep 29 | 17 | R · Representative |
Our ordinary calendar model requires supported dates and standard/representative source quality with at least 10 years. This does not erase local uncertainty.
Places using this nearby reference
Connections are based on Census internal points and straight-line distance.