When to plant in Los Altos, CA
USDA Zone 9bHere are the average frost dates, USDA hardiness zone, and a month-by-month planting calendar for Los Altos, California — all computed from Los Altos's nearest NOAA weather station.
With about 351 frost-free days, Los Altos supports back-to-back plantings; stagger sowings every few weeks to keep beds productive spring through fall. Zone 9b is warm enough that Los Altos can grow subtropical perennials, and the short (or absent) frost period barely limits the annual calendar.
The average first fall frost in Los Altos is now 7 days earlier than in the 1981–2010 normals. See how frost dates are shifting nationwide →
Frost probability
MOFFETT FEDERAL AIRFIELD · 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 Los Altos’s own odds, recorded at MOFFETT FEDERAL AIRFIELD.
| Threshold | SPRING 10% | SPRING 50% | SPRING 90% | FALL 10% | FALL 50% | FALL 90% |
|---|---|---|---|---|---|---|
| 36°F | Mar 6 | Feb 6 | Jan 3 | Nov 20 | Dec 6 | Dec 30 |
| 32°F | Feb 4 | Jan 6 | Dec 16 | Dec 3 | Dec 23 | Jan 16 |
| 28°F | Jan 22 | Jan 1 | Dec 16 | Dec 13 | Dec 31 | Jan 22 |
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 Los Altos, drawn to the day from the local frost dates. The dashed line is today.
Nearby weather stations
3 within 10 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.
Los Altos planting FAQ
When is the last spring frost in Los Altos, CA?
Los Altos's average last spring frost falls near January 6 — the 50% mark at 32°F in the 1991–2020 normals. Hold tender transplants until the risk has passed, then plant out.
When is the first fall frost in Los Altos, CA?
Expect Los Altos's first fall frost near December 23 — a 50% chance of 32°F by that date. Bring in or cover tender crops ahead of it.
What hardiness zone is Los Altos in?
Los Altos is in USDA hardiness zone 9b. In zone 9b, winters are mild — many tender perennials overwinter here.
How long is the growing season in Los Altos?
There are roughly 351 frost-free days in Los Altos (a long growing season), running from the average last frost around January 6 to the first fall frost near December 23.
When should I plant tomatoes in Los Altos?
In Los Altos, start tomato seeds indoors around November 11–November 25, then transplant seedlings outdoors around January 13 once the danger of frost has passed.
Never miss a window in Los Altos
An email when it’s time to start seeds, transplant, and sow — timed to Los Altos’s frost dates. Double opt-in, one-click unsubscribe, no spam.
Nearby cities
8 within reach- Mountain View · 4 km
- Palo Alto · 5 km
- Sunnyvale · 7 km
- Cupertino · 7 km
- Stanford · 9 km
- Santa Clara · 11 km
- East Palo Alto · 11 km
- Saratoga · 13 km
Frost dates recorded at MOFFETT FEDERAL AIRFIELD, 6 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 Los Altos, CA — Frost Dates & Zone 9b." Frost normals: NOAA NCEI U.S. Climate Normals 1991–2020, station USW00023244. Retrieved from https://blissgarden.com/california/los-altos.