Grass Valley, CA planting zone & frost dates
Grass Valley is in USDA hardiness zone 9a. The last spring frost usually comes around April 10 and the first fall frost around November 13, for a growing season of about 215 days.
Planting calendar for Grass Valley
Dates are counted from the average last spring frost (April 10) using the typical timing recommended by U.S. extension services. Warm-season crops go out only after the danger of frost has passed and the soil has warmed.
| Crop | When |
|---|---|
| Tomatoes | Start seeds indoors: Feb 13 – Feb 27 Transplant outdoors: Apr 17 – Apr 24 |
| Peppers | Start seeds indoors: Jan 30 – Feb 13 Transplant outdoors: Apr 24 – May 1 |
| Eggplant | Start seeds indoors: Jan 30 – Feb 13 Transplant outdoors: Apr 24 – May 1 |
| Broccoli | Start seeds indoors: Jan 30 – Feb 13 Transplant outdoors: Mar 13 – Mar 27 |
| Cabbage | Start seeds indoors: Jan 30 – Feb 13 Transplant outdoors: Mar 13 – Mar 27 |
| Onions (sets) | Plant outdoors: Mar 13 – Mar 27 |
| Peas | Sow outdoors: Feb 27 – Mar 13 |
| Spinach | Sow outdoors: Feb 27 – Mar 13 |
| Lettuce | Sow outdoors: Mar 13 – Mar 27 |
| Carrots | Sow outdoors: Mar 13 – Mar 27 |
| Potatoes | Plant outdoors: Mar 13 – Mar 27 |
| Beans | Sow outdoors: Apr 17 – Apr 24 |
| Sweet corn | Sow outdoors: Apr 17 – Apr 24 |
| Cucumbers | Sow outdoors: Apr 17 – Apr 24 |
| Squash & zucchini | Sow outdoors: Apr 17 – Apr 24 |
| Basil | Start seeds indoors: Feb 27 – Mar 13 Transplant outdoors: Apr 17 – Apr 24 |
Fall garden: cool-season crops like lettuce, spinach and kale can be sown again around Sep 18 (8 weeks before the average first fall frost on Nov 13).
Useful for zone 9a gardens
- Seed starting kit with dome — to start seeds indoors before the last frost
- LED grow light for seedlings — stops leggy seedlings
- Frost cloth / plant covers — for late spring and early fall frosts
- Soil thermometer — warm-season crops need soil above 60°F
- Shade cloth — for hot summers
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Frost risk in detail
| 90% chance | 50% chance | 10% chance | |
|---|---|---|---|
| Last 32°F frost in spring is after | Mar 17 | Apr 10 | Apr 30 |
| First 32°F frost in fall is before | Dec 1 | Nov 13 | Oct 26 |
How to read it: in spring there is a 10% chance of a frost after April 30, so that is a safe date for tender plants. In fall there is a 10% chance of frost before October 26. A hard freeze (28°F) usually ends around March 9.
Hardiness zone by ZIP code in Grass Valley
- 95945 zone 9a
- 95949 zone 9b
Nearby cities
- North Auburn zone 9b, last frost Feb 25
- Auburn zone 9b, last frost Feb 25
- Lincoln zone 9a, last frost Feb 11
- Rocklin zone 9b, last frost Jan 12
- Granite Bay zone 9b, last frost Feb 25
- Linda zone 9b, last frost Feb 11
- Olivehurst zone 9b, last frost Feb 11
- Roseville zone 9b, last frost Jan 12
Questions
What growing zone is Grass Valley, CA?
Grass Valley is in USDA Plant Hardiness Zone 9a (average extreme winter low 20°F to 25°F), according to the USDA 2023 map. Some ZIP codes of the city fall in zone 9b.
When is the last frost in Grass Valley?
The average last spring frost (32°F) in Grass Valley is April 10. There is still a 10% chance of frost until April 30.
When can I plant tomatoes in Grass Valley?
Transplant tomatoes outdoors 1–2 weeks after the average last frost: around Apr 17 – Apr 24. Start seeds indoors 6–8 weeks before the last frost.
Frost dates: NOAA U.S. Climate Normals 1991–2020, station Grass Valley #2, CA (USC00043573), 1.8 km (1.1 mi) from the city center, elevation 732 m, based on 25 years of records. Hardiness zone: USDA Plant Hardiness Zone Map 2023 for the ZIP code nearest to the city center. Microclimates (valleys, hills, cities, coasts) can be warmer or colder: check the local forecast before planting. How we calculate the data.