California Frost Dates & Growing Season Guide
California (CA) spans USDA hardiness zones 10a, 10b, 9a, 9b, with growing seasons ranging from 280 days in Fresno to 365 days in San Diego. The average growing season across the state is approximately 327 days.
California City Frost Dates
The table below shows the average last spring frost date, first fall frost date, growing season length, and USDA hardiness zone for each city. Click a city name for detailed planting calendars and zone information.
| City | Last Spring Frost | First Fall Frost | Growing Season | Zone | Min Temp |
|---|---|---|---|---|---|
| Los Angeles | January 3 | December 25 | 356 days | 10a | 30°F |
| San Francisco | January 10 | December 15 | 339 days | 10a | 30°F |
| Sacramento | February 10 | December 1 | 294 days | 9b | 25°F |
| San Diego | January 1 | December 31 | 365 days | 10b | 35°F |
| Fresno | February 18 | November 25 | 280 days | 9a | 20°F |
Planting Windows for California
Based on average frost dates, here are the recommended planting windows for each city. The indoor seed start date is approximately seven weeks before the last spring frost. Transplanting should occur about two weeks after the last frost. The last direct sow date for fall crops is ten weeks before the first fall frost.
| City | Start Seeds Indoors | Transplant After | Last Direct Sow |
|---|---|---|---|
| Los Angeles | November 15 | January 17 | October 16 |
| San Francisco | November 22 | January 24 | October 6 |
| Sacramento | December 23 | February 24 | September 22 |
| San Diego | November 13 | January 15 | October 22 |
| Fresno | December 31 | March 3 | September 16 |
Gardening in California
California's extraordinary climate diversity means gardening practices vary dramatically by region. Coastal Southern California (zones 10a-10b) is nearly frost-free and can grow tropical and subtropical plants year-round. The Central Valley offers a long, hot growing season ideal for commercial-scale tomatoes, stone fruits, and grapes. Northern California mountains can see frost into June. Regardless of region, water conservation is critical: drip irrigation, mulching, and drought-tolerant plant selection are standard practices. Mediterranean herbs like rosemary, lavender, and thyme are naturals for much of the state.
Understanding California's Hardiness Zones
California includes USDA hardiness zones 10a, 10b, 9a, 9b. These zones indicate the average annual extreme minimum winter temperature for each area, which determines which perennial plants, trees, and shrubs can survive winter without protection. When purchasing trees, shrubs, or perennial flowers, always check that the plant is rated for your hardiness zone or a lower (colder) zone number.
Tips for Using California Frost Dates
These frost dates represent long-term averages and should be treated as guidelines rather than guarantees. In any given year, the actual last spring frost or first fall frost may arrive one to three weeks earlier or later than the average. Factors that affect your specific location include elevation above the city center, proximity to water, slope direction, and whether you are in an urban or rural area. South-facing slopes and areas near large pavement or building masses tend to be warmer than surrounding open land. Low-lying valleys and exposed hilltops are often colder than mid-slope positions.
To protect against late spring frosts, keep row cover fabric, old bed sheets, or frost blankets on hand. Monitor your local weather forecast daily as the average frost date approaches. When frost is predicted after you have transplanted, covering plants in the late afternoon traps ground heat and can protect against temperatures down to about 28 degrees Fahrenheit. For fall season extension, the same covers protect mature plants from early frosts, often buying several additional weeks of harvest.