USDA Hardiness Zone 9b
Frost Dates for 95138 — San Jose, California
NOAA 1991–2020 normals from Mt Hamilton, CA (4,206 ft), 10 miles northeast.
Updated
In San Jose, the last spring frost (32°F) is around May 3 in half of years and has passed by June 5 in nine years out of ten. The first fall frost comes around November 18, as early as October 22 one year in ten, leaving a typical freeze-free season of 197 days (NOAA, Mt Hamilton, CA).
- Last spring frost
- May 3
- First fall frost
- November 18
- Growing season
- 197 days
- Hardiness zone
- 9b
50% probability
50% probability
freeze-free, 50%
25 to 30°F (-3.9 to -1.1°C) coldest night
- First snow
- December 19
- Last snow
- April 15
- Winters with snow
- 100%
- Snow per year
- 18.1"
median, 1991–2020
median, 1991–2020
20 of 20 observed
NOAA normal
Frost risk by date in San Jose
Half of springs at Mt Hamilton, CA see their last 32°F night by May 3; only one in ten is past it by April 7, and one in ten still has one after June 5. Planting tender crops after May 16 leaves a 30% risk of a frost on them, after May 26 20%, and after June 5 10%. The 33 days between the even-odds date and the one-in-ten date is wider than at 61% of the 220 California stations behind this site's ZIP pages, so a fixed calendar date is a gamble here.
In fall the first 32°F night comes by November 18 in half of years, as early as October 22 one year in ten, and holds off past December 12 one year in ten. A hard freeze of 28°F follows 19 days later, around December 7; in spring the one-in-ten date for 28°F is May 6, 30 days before the 32°F one. The freeze-free season lasts 197 days in a typical year, shorter than at 81% of the 219 California stations; it reaches 235 days one year in ten and falls short of 157 one year in ten. On average 45 nights a year drop to 32°F or below. Nights of 36°F, when frost can still settle on leaves in low, open spots, continue 24 days longer, to about May 27, and return around October 29. Nights of 24°F, cold enough to damage hardier plants, come in 86% of winters and 16°F in 7%.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Apr 28 | May 7 | May 14 | May 21 | May 27 | May 31 | Jun 4 | Jun 9 | Jun 18 |
| 32°F | Apr 7 | Apr 17 | Apr 24 | Apr 29 | May 3 | May 9 | May 16 | May 26 | Jun 5 |
| 28°F | Feb 23 | Mar 14 | Mar 27 | Apr 3 | Apr 10 | Apr 15 | Apr 22 | Apr 29 | May 6 |
| 24°F86% of yrs | Dec 31 | Jan 18 | Feb 6 | Feb 21 | Mar 1 | Mar 13 | Mar 25 | Apr 1 | Apr 11 |
| 20°F38% of yrs | too rare for a date | ||||||||
| 16°F7% of yrs | too rare for a date | ||||||||
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Oct 1 | Oct 10 | Oct 17 | Oct 22 | Oct 29 | Nov 3 | Nov 8 | Nov 15 | Nov 23 |
| 32°F | Oct 22 | Nov 1 | Nov 7 | Nov 13 | Nov 18 | Nov 25 | Dec 1 | Dec 4 | Dec 12 |
| 28°F | Nov 10 | Nov 20 | Nov 29 | Dec 3 | Dec 7 | Dec 12 | Dec 20 | Jan 1 | Jan 18 |
| 24°F86% of yrs | Nov 28 | Dec 7 | Dec 15 | Dec 26 | Jan 1 | Jan 10 | Jan 23 | Feb 8 | Mar 2 |
| 20°F38% of yrs | too rare for a date | ||||||||
| 16°F7% of yrs | too rare for a date | ||||||||
Freeze probabilities 1991–2020 at Mt Hamilton, CA, from NOAA NCEI U.S. Climate Normals. Where a temperature is reached in fewer than 99.5% of years, the dates describe only the years that reach it. Not a forecast.
Frost risk on any date in 95138 →Compare San Jose with another place →
Weather by month in San Jose
July is the warmest month at Mt Hamilton, CA, averaging 79°F by day and 65°F at night; February is the coldest at 49°F and 38°F. A freezing night is all but certain in every month from December to January (a 90% chance or more). From July to September the chance of a 32°F night stays under 10% each month.
Warmth for growing adds up to 3,173 growing degree days a year (base 50°F), fewer than at 81% of the 283 California stations. 27% of them (857) have built up by the end of June, and July adds the most, 679. Precipitation totals 27.3 inches a year, most in January (5.0") and least in July (0.0"); May to September bring 7% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 50 | 39 | 5.0 | 92% | 8 | 46 |
| Feb | 49 | 38 | 4.8 | 90% | 8 | 35 |
| Mar | 51 | 39 | 4.4 | 89% | 8 | 54 |
| Apr | 55 | 41 | 2.2 | 86% | 7 | 90 |
| May | 62 | 47 | 1.3 | 48% | 2 | 214 |
| Jun | 71 | 56 | 0.3 | 14% | 0 | 418 |
| Jul | 79 | 65 | 0.0 | 0% | 0 | 679 |
| Aug | 79 | 65 | 0.1 | 0% | 0 | 668 |
| Sep | 75 | 60 | 0.2 | 0% | 0 | 526 |
| Oct | 66 | 52 | 1.3 | 17% | <1 | 309 |
| Nov | 55 | 43 | 3.0 | 62% | 4 | 102 |
| Dec | 49 | 38 | 4.7 | 94% | 9 | 33 |
Monthly normals 1991–2020 at Mt Hamilton, CA (4,206 ft), NOAA NCEI. "32°F night": chance of at least one in the month. GDD: growing degree days, base 50°F.
Compared with the next station
The nearest other station, San Jose, CA, 10 miles northwest of San Jose and 4,139 feet lower, has a last frost 121 days earlier (January 2), a first frost 37 days later (December 25), a season 165 days longer.
When it snows in San Jose, California
The first measurable snow (0.1 inch or more) in San Jose usually arrives around December 19, and the last of the season around April 15. Those are the middle dates across the winters of 1991–2020 at Mt Hamilton, CA, 9.5 miles away: half of years saw snow earlier, half later. Every one of those winters saw snow. The last 32°F night of spring typically comes 18 days after the last snow.
Planting calendar for 95138
| When | What to do |
|---|---|
| February 22 – March 8 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| March 8 – March 22 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| April 5 – April 19 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| May 3 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by August 26 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by November 4 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| November 18 onward | Plant garlic, mulch beds, lift tender bulbsGarlic wants a cold spell; bare soil loses structure over winter. |
The weeks before and after the 50% dates are general rules of thumb, not NOAA figures; a seed packet gives the timing for each variety.
Where these figures come from
ZIP 95138 is 10 miles from Mt Hamilton, CA, which stands at 4,206 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 3 other ZIP codes share the station; its figures are presented in full for 95135 (San Jose). The 2023 USDA Plant Hardiness Zone Map lists ZIP 95138 in zone 9b, the band where the coldest night of the year averaged 25 to 30°F (-3.9 to -1.1°C) over 1991–2020; a zone describes winter lows, not frost dates.
Frost dates across California →
Hardiness zone and temperature range: USDA Plant Hardiness Zone Map 2023 (USDA-ARS, Oregon State University), ZIP-code listing, unchanged. °C converted from °F by this site.
Thirty-year averages, not a forecast: check the forecast before planting out. How stations are matched and which pages are offered to search engines: methodology.