Frost Dates for San Marino, CA 91108
Last spring frost January 11 · First fall frost January 5 · 359 frost-free days · USDA Zone 10a
Frost probability for 91108
| Frost | 10% | 50% | 90% |
|---|---|---|---|
| Spring (last frost) | February 20 | January 11 | — |
| Fall (first frost) | December 1 | January 5 | — |
Dates come from NOAA 1971–2000 freeze probabilities at the nearest reporting station (4.4 km away); the 50% date is the median year.
Month by month in San Marino
| Month | What to do |
|---|---|
| January | Plant cool-season crops: lettuce, spinach, broccoli, peas, and carrots. |
| February | Direct sow brassicas and root vegetables. Start warm-season seedlings indoors. |
| March | Transplant warm-season crops outdoors. Sow beans, cucumbers, and squash. |
| April | Main warm-season planting window. Direct sow melons and sweet corn. |
| May | Succession plant lettuce. Keep beds irrigated as temperatures climb. |
| June | Monitor for heat stress. Harvest zucchini and cucumbers frequently. |
| July | Harvest regularly to encourage continued production. Watch for pests. |
| August | Start fall cool-season crops: broccoli, kale, beets, and carrots. |
| September | Plant fall lettuce, spinach, arugula, and radishes. |
| October | Harvest mature crops. Direct sow cold-tolerant greens. |
| November | Plant garlic and onion sets. Harvest cool-season crops through the month. |
| December | Plant cool-season crops for winter harvest. Plan next year's garden. |
What grows in a 359-day season
Frequently Asked Questions
What is the last frost date for San Marino, CA (ZIP 91108)?
The median last spring frost date for San Marino, CA (ZIP code 91108) is around January 11. This is the 50th-percentile date — meaning half of all years see frost end before this date. Use the 10% and 90% dates to understand the full range of risk in your area.
What is the first fall frost date in San Marino, CA?
The median first fall frost date for San Marino, CA is around January 5. Plan to harvest or protect frost-sensitive crops like tomatoes and peppers at least a week before this date to avoid losses.
How long is the growing season in San Marino, CA?
The frost-free growing season in San Marino is about 359 days. This window — from your last spring frost to your first fall frost — is when warm-season vegetables thrive. Cold-hardy crops like kale, spinach, and peas can extend your season by weeks on either side.
What USDA hardiness zone is San Marino, CA?
Based on frost date patterns, San Marino falls approximately in 10a. USDA hardiness zones are determined by average annual minimum winter temperatures and guide both plant selection and planting timing for your location.
When should I start tomatoes indoors in San Marino, CA?
Start tomato seeds indoors 6–8 weeks before your last frost date (around January 11). For San Marino, that's roughly November 16 to November 30. Transplant outdoors 1–2 weeks after your last frost.
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