San Jose, California Frost Dates, Growing Season & Hardiness Zone

When is the last frost in San Jose?

Not every winter freezes here. NOAA puts the chance of at least one 32°F night in a year at 56.2% at San Jose. The dates on this page describe the years that do freeze (NOAA computes them as conditional probabilities).

In the years that freeze, half have their last 32°F night by Jan 2, and 1 in 10 of them still has one after Jan 23. Nights of 36°F (frost possible on plants) come in 95.3% of years and typically end around Jan 26. A 28°F hard freeze comes in 8.4% of years.

San Jose has a long late-frost tail: 21 days separate the typical date (Jan 2) from the safer 1-in-10 date (Jan 23). If tender plants go out early, be ready to protect them on cold nights.

In years with a freeze, the typical last 32°F night comes around Jan 2, and the typical last 36°F night (frost possible on plants in low spots) around Jan 26, 24 days later. On clear, calm nights, frost can form on leaves even when the thermometer reads above freezing.

Is it too early to plant in San Jose?

Before Jan 2 the odds of another 32°F night are better than even; after Jan 23 they are about 1 in 10 or less.

Today's risk is computed in your browser from the same NOAA probability table, shown as the range between the two nearest NOAA probability levels.

When is the first frost in San Jose?

In the years that freeze, half have their first 32°F night by Dec 25, and 1 in 10 of them has one as early as Dec 4. The first 36°F night (frost possible on plants) typically comes around Dec 10. A 28°F hard freeze comes in 8.4% of years.

Fall plantings are timed backward from first frost: Dec 25 typically, or Dec 4 if you want a cushion. See the planting calendar for each crop's date.

How long is San Jose's growing season?

San Jose's frost-free season (32°F) typically runs 362 days. In about 1 year out of 10, it's shorter than 335 days.

This much frost-free time means many crops can go in twice, in spring and again for a fall harvest.

Each year the station logs an average of 4,309 growing degree days (base 50°F), a measure of the heat available for crop growth.

How does San Jose's season compare?

At 362 days, the typical frost-free season in San Jose is the longest among the 3 California cities with frost dates on this site.

No U.S. city with frost dates on this site has a longer typical frost-free season than San Jose, at 362 days. Of the 56 cities we compare, the season is shorter in 55.

Growing degree days (base 50°F)

Annual normal: 4,309 GDD (NOAA flag R, 12 years). Running total by the end of each month (sum of NOAA daily GDD normals, so the year-end total can differ slightly from the annual normal):

What growing zone is San Jose? (USDA 2023)

The 2023 USDA map puts San Jose in zone 9b–10a (25 to 35°F average coldest winter night). On the 2012 map, most of the city was 9b. Comparing ZIPs listed in both tables, 3 of 39 moved up half a zone.

Zones: PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed 2026-10-08. Shown as published in the ZIP tables; this page does not show a zone map. Not the official USDA Plant Hardiness Zone Map (official map: planthardiness.ars.usda.gov).

Does the new zone change San Jose's frost dates?

No. A hardiness zone reflects only the average coldest winter temperature, not the timing of spring or fall frost. San Jose's frost dates come from NOAA's 1991–2020 frost probabilities, and the 2023 zone map didn't change them. Pick perennials that survive winter by zone; time your planting by frost dates.

Why do San Jose frost dates differ between websites?

Some sources list Jan 10 for San Jose. That's the 30%-risk date: about 3 in 10 years with a freeze still have a 32°F night after it. Our headline date is Jan 2, the 50% (median) date.

Jan 23 is the 10%-risk, or 'safer', date: only about 1 in 10 years with a freeze has a 32°F night after it.

Jan 26 is the 50% date for a 36°F night (frost possible on plants), not a 32°F freeze. Sites that treat 36°F as the danger line show later dates.

Sites also pick different weather stations. Within 25 miles of the city center, the 10 stations that meet our quality rules put the typical (50%) last 32°F frost anywhere from Jan 1 to Mar 25 (table below).

Which weather station is this based on?

Station

San Jose (NOAA USC00047821, COOP)

Distance

6.1 mi NW of the city center

Elevation

67 ft; city center 163 ft (USGS), difference −96 ft

Record

NOAA completeness flag R, 17 of 30 years (1991–2020)

Confidence

Medium (rule)

Confidence: Medium. The station passes our quality rules, but it's farther away or at a different elevation than ideal (6.1 mi, −96 ft; NOAA flag R, 17 of 30 years).

Caveat: NOAA flags this station's frost statistics 'R' (representative). They rest on 17 of the 30 years in 1991–2020, with missing months filled in from surrounding stations. The nearest station with a full 'S' (standard) record is Newark, 19.3 mi away; its typical last frost is Jan 1.

San Jose planting dates at a glance

Balanced dates use the 30%-risk last-frost date as the anchor. The San Jose planting calendar has typical and safe dates, fall planting and a month-by-month list for 26 vegetables.

When to plant tomatoes in San Jose · Fall planting dates for San Jose

Frost dates near San Jose

All California cities

Frequently asked questions

What is the average last frost date in San Jose?

Not every winter in San Jose freezes: NOAA puts the yearly chance of a 32°F night at San Jose at 56.2%. In the years that do freeze, the typical (50%) last one is Jan 2, and only about 1 in 10 of those years has one after Jan 23.

When is the first frost in San Jose?

Not every year has one: NOAA's yearly chance of a 32°F night at San Jose is 56.2%. In the years with a freeze, the first typically comes by Dec 25; in about 1 in 10 of them, by Dec 4.

What growing zone is San Jose, California?

Zone 9b–10a. Most of San Jose was 9b on the 2012 map too, but 3 of 39 city ZIPs changed zone.

Is it too early to plant in San Jose?

For frost-tender plants, it's early before Jan 2. If you plant before then, another 32°F night after your planting day is more likely than not in years with a freeze. Between Jan 2 and Jan 23, that risk falls from 50% to 10% of freeze years. NOAA puts the yearly chance of any 32°F night at San Jose at 56.2%. Cool-season crops like peas and lettuce can go in weeks earlier; see the planting calendar.

What temperature is a killing frost?

A light frost is enough to kill tender crops such as tomatoes. CSU Extension describes 28–32°F as a light frost and anything below 28°F as a heavy frost. We report NOAA odds at three thresholds: 36°F (frost possible on plants), 32°F (freeze, our headline) and 28°F (hard freeze).

Is first frost the same as first freeze?

Not quite. A 'freeze' means the air reached 32°F. 'Frost' is ice on surfaces, and it can form on calm, clear nights even when the air is a few degrees above freezing. In San Jose, the first 36°F night (frost possible on plants) typically comes around Dec 10. A 32°F night doesn't come every year here: NOAA puts the yearly chance at 56.2%. In years with a freeze, the first one typically comes around Dec 25.

Download & sources

• Add San Jose frost & planting dates to your calendar (.ics, 2027)
• Printable planting calendar (PDF)
• How these numbers are calculated

Data: NOAA NCEI U.S. Climate Normals 1991–2020 (annual/seasonal and daily normals, station USC00047821); USDA Plant Hardiness Zone ZIP tables 2023 and 2012 by the PRISM Group, Oregon State University; Census 2020 ZIP/place relationship file; USGS elevation. Long-term odds, not a forecast. Figures and sentences are generated from these data by fixed rules; see the methodology. Last updated 2026-10-08.