When to plant in Costa Mesa, CA
USDA Zone 10bEverything below — frost dates, hardiness zone, and what to plant when in Costa Mesa, California — is derived from the closest NOAA station with complete climate normals.
With about 354 frost-free days, Costa Mesa supports back-to-back plantings; stagger sowings every few weeks to keep beds productive spring through fall. These dates come from a station roughly 15 km away, the closest with full normals; terrain around Costa Mesa (elevation, water, pavement) can move your real frost dates a few days either way. Zone 10b is warm enough that Costa Mesa can grow subtropical perennials, and the short (or absent) frost period barely limits the annual calendar.
Frost probability
TUSTIN IRVINE RCH · 1991–2020The date the last spring and first fall frost occur, by threshold and probability. A 90% date is later in spring — and earlier in fall — than a 10% date; the 50% · 32°F row is what most gardeners plan around. These are Costa Mesa’s own odds, recorded at TUSTIN IRVINE RCH.
| Threshold | SPRING 10% | SPRING 50% | SPRING 90% | FALL 10% | FALL 50% | FALL 90% |
|---|---|---|---|---|---|---|
| 36°F | Mar 5 | Feb 1 | Jan 3 | Nov 24 | Dec 13 | Jan 8 |
| 32°F | Feb 2 | Jan 5 | Dec 14 | Dec 3 | Dec 25 | Jan 20 |
Download this table as CSV ↓ — every threshold and probability, plus this city’s planting-window dates.
What to plant now
TODAY · JULY 19Nothing new to sow or transplant outdoors in the next few weeks — a seasonal lull. Check the full-year calendar below for the next window.
Full-year planting calendar
Each bar is the exact window to take a planting action in Costa Mesa, drawn to the day from the local frost dates. The dashed line is today.
Nearby weather stations
3 within 42 km · complete 32°F normalsWhen stations disagree by more than a few days, that spread is real microclimate variation — elevation, water, urban heat. Judge which station best matches your own yard.
Costa Mesa planting FAQ
When is the last spring frost in Costa Mesa, CA?
On average, the last spring frost in Costa Mesa is around January 5 (50% probability at 32°F, from 1991–2020 NOAA normals). Wait until after this date to set out tender plants like tomatoes and peppers.
When is the first fall frost in Costa Mesa, CA?
The first fall frost in Costa Mesa typically arrives around December 25 (50% probability at 32°F). Harvest or protect frost-sensitive crops before then.
What hardiness zone is Costa Mesa in?
Costa Mesa is in USDA hardiness zone 10b. In zone 10b, winters are mild — many tender perennials overwinter here.
How long is the growing season in Costa Mesa?
There are roughly 354 frost-free days in Costa Mesa (a long growing season), running from the average last frost around January 5 to the first fall frost near December 25.
When should I plant tomatoes in Costa Mesa?
In Costa Mesa, start tomato seeds indoors around November 10–November 24, then transplant seedlings outdoors around January 12 once the danger of frost has passed.
Never miss a window in Costa Mesa
An email when it’s time to start seeds, transplant, and sow — timed to Costa Mesa’s frost dates. Double opt-in, one-click unsubscribe, no spam.
Nearby cities
8 within reach- Fountain Valley · 6 km
- Newport Beach · 6 km
- Santa Ana · 8 km
- Huntington Beach · 9 km
- Tustin · 12 km
- Westminster · 12 km
- Irvine · 13 km
- Garden Grove · 13 km
Frost dates recorded at TUSTIN IRVINE RCH, 15 km from the city center · 1991–2020 NOAA climate normals · zone from the USDA/PRISM 2023 map. How we compute this.
BlissGarden. "When to Plant in Costa Mesa, CA — Frost Dates & Zone 10b." Frost normals: NOAA NCEI U.S. Climate Normals 1991–2020, station USC00049087. Retrieved from https://blissgarden.com/california/costa-mesa.