Frost dates for 92143San Ysidro, CA
The average last spring frost in San Ysidro is March 27 and the average first fall frost is December 1, giving a typical growing season of about 248 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- Mar 27
- Average first fall frost
- Dec 1
- Growing season
- 248 days
Safer after Apr 30 (1-in-10 risk)
Possible by Nov 3 (1-in-10 risk)
First frost typically in 35 days
Frost risk by date
NOAA reports frost dates as probabilities. The middle date is the average (a 50% chance). For spring, the 10% date is a safer planting date: frost after it happens in about 1 year in 10. Light frost (36°F) can damage tender plants; a hard freeze (28°F) kills most annuals.
| Temperature | Last spring: 90% / 50% / 10% chance | First fall: 10% / 50% / 90% chance | Growing season (50%) | Years with at least one |
|---|---|---|---|---|
| Light frost (36°F) | Mar 29 · Apr 27 · May 23 | Oct 17 · Nov 11 · Dec 3 | 199 days | 100% |
| Frost / freeze (32°F) | Feb 17 · Mar 27 · Apr 30 | Nov 3 · Dec 1 · Dec 21 | 248 days | 100% |
| Hard freeze (28°F) | Jan 1 · Feb 13 · Mar 24 | Nov 23 · Dec 22 · Feb 3 | 309 days | 94% |
Planting calendar for San Ysidro
Planting windows from the University of Maryland Extension calendar, shifted to your average frost dates. Use them as a starting point and adjust for seed packet instructions and local conditions.
| Crop | Task | Window |
|---|---|---|
| Tomatoes | Start seeds indoors | Feb 24 – May 2 |
| Tomatoes | Transplant outdoors | Apr 12 – Aug 11 |
| Peppers | Start seeds indoors | Feb 24 – Mar 27 |
| Peppers | Transplant outdoors | Apr 26 – May 27 |
| Eggplant | Start seeds indoors | Mar 13 – Apr 11 |
| Eggplant | Transplant outdoors | Apr 26 – May 27 |
| Cucumbers | Sow outdoors | Apr 26 – Aug 21 |
| Summer squash | Sow outdoors | Apr 12 – May 27 |
| Winter squash & pumpkins | Sow outdoors | Apr 26 – May 27 |
| Snap beans | Sow outdoors | Apr 12 – Sep 13 |
| Sweet corn | Sow outdoors | Apr 12 – Aug 11 |
| Watermelon & cantaloupe | Sow outdoors | Apr 26 – May 27 |
| Okra | Sow outdoors | Apr 19 – May 12 |
| Peas | Sow outdoors (spring) | Feb 24 – Apr 11 |
| Potatoes | Plant outdoors (spring) | Feb 24 – Apr 26 |
| Onions | Start seeds indoors (spring) | Jan 13 – Feb 9 |
| Onions | Transplant outdoors (spring) | Mar 13 – Apr 11 |
| Broccoli | Start seeds indoors (spring) | Feb 6 – Mar 12 |
| Broccoli | Transplant outdoors (spring) | Mar 13 – Apr 11 |
| Broccoli | Start seeds indoors (fall) | Aug 1 – Aug 11 |
| Broccoli | Transplant outdoors (fall) | Aug 31 – Sep 11 |
| Cabbage | Start seeds indoors (spring) | Jan 27 – Feb 24 |
| Cabbage | Transplant outdoors (spring) | Feb 24 – Mar 27 |
| Cabbage | Start seeds indoors (fall) | Jul 22 – Aug 21 |
| Cabbage | Transplant outdoors (fall) | Aug 21 – Sep 21 |
| Leaf lettuce | Sow outdoors (spring) | Feb 24 – May 12 |
| Leaf lettuce | Sow outdoors (fall) | Aug 21 – Oct 7 |
| Spinach | Sow outdoors (spring) | Feb 17 – Apr 2 |
| Spinach | Sow outdoors (fall) | Sep 7 – Oct 12 |
| Radishes | Sow outdoors (spring) | Feb 24 – Apr 16 |
| Radishes | Sow outdoors (fall) | Aug 21 – Oct 22 |
| Kale | Sow outdoors (spring) | Mar 13 – Apr 2 |
| Kale | Sow outdoors (fall) | Aug 14 – Sep 21 |
| Carrots | Sow outdoors (spring) | Mar 27 – May 12 |
| Carrots | Sow outdoors (fall) | Jul 22 – Sep 6 |
| Garlic | Plant outdoors (fall) | Nov 21 – Dec 22 |
Where these dates come from
ZIP code 92143 is matched to the NOAA station Julian Cdf, CA, 20 km away, at 4,215 ft elevation (196 ft higher than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Julian Cdf, CA (used) | 4,215 ft | Mar 27 | Dec 1 |
| Borrego Desert Park, CA | 810 ft | Jan 10 | Jan 1 |
| Henshaw Dam, CA | 2,700 ft | Apr 18 | Oct 26 |
| Palomar Mtn Obsy, CA | 5,550 ft | Apr 29 | Nov 18 |
Frost dates near San Ysidro
- Ranchita, CA 92066 · last Mar 27, first Dec 1
- Warner Springs, CA 92086 · last Apr 18, first Oct 26
- Santa Ysabel, CA 92070 · last Apr 18, first Oct 26
- Borrego Springs, CA 92004 · last Jan 10, first Jan 1
- Julian, CA 92036 · last Mar 27, first Dec 1
- Palomar Mountain, CA 92060 · last Apr 29, first Nov 18
- Aguanga, CA 92536 · last Apr 18, first Oct 26
- Ramona, CA 92065 · last Mar 19, first Nov 23
Frequently asked questions
- When is the last frost in San Ysidro, CA?
- For ZIP code 92143, the average last spring frost (32°F) is March 27, based on NOAA 1991-2020 climate normals for the Julian Cdf, CA weather station. There is a 1-in-10 chance of a frost after April 30.
- When is the first frost in San Ysidro, CA?
- The average first fall frost (32°F) is December 1. There is a 1-in-10 chance of frost by November 3, so tender plants are at risk from that point on.
- How long is the growing season in 92143?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 248 days long.
- Are these frost dates a forecast?
- No. They are 30-year averages and probabilities from NOAA weather station records. Use them to plan, then watch your local forecast before planting tender crops or leaving them uncovered.