Frost Dates for San Mateo, CA 94403
Last spring frost Frost-free zone · First fall frost Frost-free zone · 365 frost-free days · USDA Zone 10a
Frost probability for 94403
| Frost | 10% | 50% | 90% |
|---|---|---|---|
| Spring (last frost) | February 28 | — | — |
| Fall (first frost) | December 9 | — | — |
Dates come from NOAA 1971–2000 freeze probabilities at the nearest reporting station (10.5 km away); the 50% date is the median year.
Frost dates by ZIP code in San Mateo, CA
| ZIP | Last spring frost (50%) | First fall frost (50%) | Zone |
|---|---|---|---|
| 94403 | — | — | 10a |
| 94404 | January 28 | December 11 | 10a |
| 94401 | — | — | 10a |
| 94402 | — | — | 10a |
Month by month in San Mateo
| 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 365-day season
Frequently Asked Questions
What is the last frost date for San Mateo, CA (ZIP 94403)?
San Mateo, CA is frost-free in most years, so there's no last spring frost date to plan around.
What is the first fall frost date in San Mateo, CA?
San Mateo, CA is frost-free in most years, so there's no first fall frost date to plan around.
How long is the growing season in San Mateo, CA?
The frost-free growing season in San Mateo is year-round. 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 Mateo, CA?
Based on frost date patterns, San Mateo 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 Mateo, CA?
San Mateo is a frost-free zone, so you can start tomatoes and transplant at any time of year. Focus on heat management rather than frost timing.
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