ROOTED IN REAL DATA Historical data. Thoughtful planning. No weather guarantees.
California · NOAA station reference

San Rafael Civic Ctr
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 reference
Modeled annual freeze occurrence: 69.8%. Date percentiles below are conditional on a cold season containing a 32°F freeze, not all years.
Last spring 32°F freeze · conditional medianJan 11
First fall 32°F freeze · conditional medianDec 21
Days between conditional medians344 days
Uncertainty, made visible

One 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.

10%Feb 25
30%Feb 1
50%Jan 11Median reference
70%Dec 30Prior year
90%Dec 14Prior year

The 10% date is later in spring than the median: a more cautious historical reference, still not a guarantee.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.

10%Dec 2
30%Dec 13
50%Dec 21Median reference
70%Jan 2Next year
90%Feb 9Next year

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.

An explicit planning choice

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.

Know the evidence

The reference
behind the numbers.

Official station name
SAN RAFAEL CIVIC CTR, CA US
NOAA station ID
USC00047880
Coordinates
37.9983, -122.5372
Station elevation
36.6 m / 120 ft
Normal period
1991–2020
Source retrieved
2026-10-02
Source modified
Tue, 27 Jun 2023 15:16:19 GMT
Original NOAA station record
Put the data in context

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.
Understand the method Check the current NWS forecast
Traceable, down to the field

How strong is this reference?

Source variableHistorical dateYearsNOAA completeness
Last spring freeze · 10%Feb 2526R · Representative
Last spring freeze · 30%Feb 126R · Representative
Last spring freeze · 50%Jan 1126R · Representative
First fall freeze · 10%Dec 226R · Representative
First fall freeze · 30%Dec 1326R · Representative
First fall freeze · 50%Dec 2126R · Representative

Our ordinary calendar model requires supported dates and standard/representative source quality with at least 10 years. This does not erase local uncertainty.

Explore the geographic connection

Places using this nearby reference

Connections are based on Census internal points and straight-line distance.

A wider view

Other California references

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