When to plant in Simi Valley, CA
USDA Zone 10aEverything below — frost dates, hardiness zone, and what to plant when in Simi Valley, California — is derived from the closest NOAA station with complete climate normals.
With about 325 frost-free days, Simi Valley supports back-to-back plantings; stagger sowings every few weeks to keep beds productive spring through fall. Simi Valley's nearest full-normals station sits about 19 km out, so treat these as a close estimate — local microclimate can nudge your first and last frost. In zone 10a, frost is a minor factor for Simi Valley — most perennials thrive, and annual vegetables can go out early and stay late.
Frost probability
WOODLAND HILLS PIERCE COLLEGE · 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 Simi Valley’s own odds, recorded at WOODLAND HILLS PIERCE COLLEGE.
| Threshold | SPRING 10% | SPRING 50% | SPRING 90% | FALL 10% | FALL 50% | FALL 90% |
|---|---|---|---|---|---|---|
| 36°F | Apr 7 | Mar 2 | Jan 30 | Nov 12 | Nov 29 | Dec 19 |
| 32°F | Mar 5 | Jan 24 | Dec 21 | Nov 27 | Dec 15 | Jan 26 |
| 28°F | Feb 1 | Dec 31 | Dec 5 | Dec 1 | Dec 26 | Jan 25 |
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 Simi Valley, drawn to the day from the local frost dates. The dashed line is today.
Nearby weather stations
3 within 21 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.
Simi Valley planting FAQ
When is the last spring frost in Simi Valley, CA?
Plan for the last spring frost in Simi Valley around January 24 (the date it has a 50% chance of a 32°F freeze). Anything frost-sensitive should go out after it.
When is the first fall frost in Simi Valley, CA?
In Simi Valley, the first 32°F freeze of fall lands around December 15 on average. Time your last harvests and any season-extension cover before it.
What hardiness zone is Simi Valley in?
Simi Valley is in USDA hardiness zone 10a. In zone 10a, winters are mild — many tender perennials overwinter here.
How long is the growing season in Simi Valley?
Simi Valley has about 325 frost-free days — a long growing season — between the average last spring frost (January 24) and first fall frost (December 15).
When should I plant tomatoes in Simi Valley?
For Simi Valley, sow tomatoes indoors about November 29–December 13 and move the seedlings out around January 31, after the last spring frost.
Never miss a window in Simi Valley
An email when it’s time to start seeds, transplant, and sow — timed to Simi Valley’s frost dates. Double opt-in, one-click unsubscribe, no spam.
Nearby cities
8 within reach- Oak Park · 9 km
- Moorpark · 12 km
- Agoura Hills · 13 km
- Thousand Oaks · 14 km
- Calabasas · 17 km
- Stevenson Ranch · 20 km
- Fillmore · 21 km
- Castaic · 26 km
Frost dates recorded at WOODLAND HILLS PIERCE COLLEGE, 19 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 Simi Valley, CA — Frost Dates & Zone 10a." Frost normals: NOAA NCEI U.S. Climate Normals 1991–2020, station USC00049785. Retrieved from https://blissgarden.com/california/simi-valley.