Harman US

Frost Dates for Sunnyvale, CA

Last spring frost
Jan 6
First fall frost
Dec 23
Growing season
353 days
Hardiness zone
10a

In an average year around Sunnyvale, CA, the last spring frost (32°F) is about Jan 6 and the first fall frost is about Dec 23, giving roughly a 353-day growing season. To be safe most years, wait until Dec 16 before setting out tender plants.

Last spring frost

Dates the last frost of spring typically ends. Plant tender crops after the risk has passed for your comfort level.

Last spring frost - Sunnyvale, CA
Frost intensity Early (10%) Average (50%) Late (90%)
Light (36°F) Mar 6 Feb 6 Jan 3
Freeze (32°F) Feb 4 Jan 6 Dec 16
Hard (28°F) Jan 22 Jan 1 Dec 16
Show full probability table (all thresholds & percentiles)
°F 10% 20% 30% 40% 50% 60% 70% 80% 90%
36°F Mar 6 Feb 27 Feb 19 Feb 12 Feb 6 Jan 31 Jan 26 Jan 15 Jan 3
32°F Feb 4 Jan 26 Jan 18 Jan 11 Jan 6 Jan 1 Dec 29 Dec 24 Dec 16
28°F Jan 22 Jan 14 Jan 8 Jan 5 Jan 1 Dec 31 Dec 27 Dec 22 Dec 16

First fall frost

Dates the first frost of fall typically arrives. Count back by a crop's days-to-maturity to know your planting cutoff.

First fall frost - Sunnyvale, CA
Frost intensity Early (10%) Average (50%) Late (90%)
Light (36°F) Nov 20 Dec 6 Dec 30
Freeze (32°F) Dec 3 Dec 23 Jan 16
Hard (28°F) Dec 13 Dec 31 Jan 22
Show full probability table (all thresholds & percentiles)
°F 10% 20% 30% 40% 50% 60% 70% 80% 90%
36°F Nov 20 Nov 25 Nov 30 Dec 2 Dec 6 Dec 10 Dec 14 Dec 19 Dec 30
32°F Dec 3 Dec 9 Dec 15 Dec 19 Dec 23 Dec 28 Jan 1 Jan 6 Jan 16
28°F Dec 13 Dec 18 Dec 24 Dec 28 Dec 31 Jan 2 Jan 8 Jan 14 Jan 22

Growing season is measured at 32°F with about 50% probability. Hardiness zone from the 2023 USDA map; frost normals from NOAA 1991-2020.

Where this data comes from

These dates are computed from the nearest official weather station with long-term records: Moffett Federal Airfield, Ca, about 2 miles away@if(!empty($station['elevation_ft'])), at 39 ft elevation. The further the station and the greater the elevation difference from your yard, the more your local frost timing can vary.

@endif
How we calculate these dates

Frost and freeze dates come from the NOAA 1991–2020 U.S. Climate Normals, the National Oceanic and Atmospheric Administration's 30-year averages for each weather station. A date shown at the 50% level is the median: in half of years the frost falls on or before it. The 10% and 90% columns show the early and late ends of the range, so you can plant on the odds you're comfortable with. These are long-term averages, not a forecast for this year - always check your local outlook before planting.

Source: NOAA National Centers for Environmental Information, 1991–2020 Climate Normals (public domain). Harman is not affiliated with or endorsed by NOAA.

Frequently asked questions

When is the last frost in Sunnyvale, CA?

On average, the last spring frost (32°F) around Sunnyvale, CA is about Jan 6. In cooler years it can run later, so for a safer bet many gardeners wait until Dec 16.

When is the first frost in the fall?

The first fall frost around Sunnyvale, CA typically arrives about Dec 23. Count back by a crop's days to maturity to find the latest date you can plant it.

When can I plant tomatoes and other tender crops?

Tender crops like tomatoes, peppers and basil are damaged by frost, so wait until the last spring frost has passed - around Jan 6 on average, or Dec 16 to be safe most years.

How long is the growing season here?

The frost-free growing season (between the last spring and first fall 32°F frost) is about 353 days in a typical year.

Are these dates a forecast for this year?

No. They are 30-year averages from the NOAA 1991–2020 Climate Normals, not a prediction for the current year. Use them for planning and always check your local weather forecast before planting or protecting crops.

Local weather for 94085 Planting calendar → California frost dates →

Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026