Frost Dates: First and last frost dates for San Gregorio, CA
ℹ️ How to read these charts for the spring
As spring unfolds, the risk of frost gradually decreases each day until your tender plants are finally safe. The probabilities shown in the chart help you make smart decisions about when to plant.
While frost typically forms at 32°F, tender plants can be damaged even when temperatures are slightly higher. Air temperatures are often measured several feet above the ground, but temperatures at plant level can be several degrees colder. Protected areas like porches help by blocking radiational cooling. Given these variables, we consider 36°F the "caution zone" for frost-sensitive plants.
Key dates for your spring planting:
- By June 3, you have a 90% chance of being frost-free — this is your "safe date" for planting tender crops
- Around May 5, there's a 50/50 chance of frost — check weather forecasts carefully if planting now
- Before April 15, there's still an 80% risk of frost — too early for tomatoes and other tender plants unless you're prepared to protect them
If the 10-day forecast shows no temperatures below 40°F, you might safely plant earlier than the above dates suggest. Many gardeners watch for this weather window to get a head start on the growing season.
| Temperature | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| Last 16° | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| Last 20° | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| Last 24° | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| Last 28° | Feb 27 | Feb 4 | Jan 14 | Dec 19 | -- | -- | -- | -- | -- |
| Last 32° | Apr 23 | Apr 5 | Mar 24 | Mar 13 | Mar 3 | Feb 21 | Feb 11 | Jan 29 | Jan 12 |
| Last 36° | Jun 3 | May 24 | May 17 | May 11 | May 5 | Apr 29 | Apr 23 | Apr 15 | Apr 5 |
ℹ️ How to read these charts for the fall
As summer ends in San Gregorio, CA, nighttime temperatures begin to drop, and your risk of frost increases with each passing day. Knowing when to expect frost helps you harvest sensitive crops and extend your growing season with protection methods.
The chart below shows the probability of experiencing specific temperatures on various dates. Here's what this means for your garden:
These probabilities help you time your end-of-season harvests and know when to apply protective measures like row covers, cloches, or cold frames to extend your harvest.
| Temperature | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| First 16° | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| First 20° | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| First 24° | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| First 28° | Dec 5 | Dec 29 | Jan 19 | Feb 14 | -- | -- | -- | -- | -- |
| First 32° | Oct 21 | Nov 4 | Nov 14 | Nov 22 | Nov 30 | Dec 9 | Dec 17 | Dec 27 | Jan 10 |
| First 36° | Oct 4 | Oct 12 | Oct 17 | Oct 22 | Oct 26 | Oct 30 | Nov 4 | Nov 10 | Nov 17 |
📍 Frost Dates for other nearby locations
- Half Moon Bay, CA 12.0 mi
- Redwood City, CA 14.1 mi
- Palo Alto, CA 17.9 mi
- San Francisco, CA 20.9 mi
- Newark, CA 26.8 mi
- Los Gatos, CA 28.7 mi
- San Francisco Oceansd, CA 30.0 mi
- San Jose, CA 30.7 mi
- San Francisco Dwtn, CA 31.7 mi
- Oakland Museum, CA 34.0 mi
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Data is provided by the NOAA National Centers for Environmental Information.