USDA Hardiness Zone 9b
Frost Dates for 94595 — Walnut Creek, California
NOAA 1991–2020 normals from Concord Wwtp, CA (40 ft), 7 miles north.
Updated
A freeze (32°F) reaches Walnut Creek in 80% of winters. When it does, the first fall frost comes around December 19 and the last spring frost around January 7; after February 1 the chance of another is under 8%.
- Last spring frost
- January 7
- First fall frost
- December 19
- Winters with a freeze
- 80%
- Hardiness zone
- 9b
50%, in freezing years
50%, in freezing years
32°F or below, 1991–2020
25 to 30°F (-3.9 to -1.1°C) coldest night
- First snow
- Rare
- Last snow
- Rare
- Winters with snow
- 0%
- Snow per year
- 0"
median, 1991–2020
median, 1991–2020
0 of 19 observed
NOAA normal
Frost risk by date in Walnut Creek
In the 80% of winters that bring a 32°F night, half of springs at Concord Wwtp, CA see their last 32°F night by January 7; only one in ten is past it by December 19, and one in ten still has one after February 1. Counting the winters with no freeze at all, the risk of a 32°F night after February 1 is under 8% and after January 7 40%. The 25 days between the even-odds date and the one-in-ten date is narrower than at 70% 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 December 19 in half of years, as early as December 1 one year in ten, and holds off past January 12 one year in ten. A hard freeze of 28°F is less common: it came in 25% of winters. The freeze-free season lasts 346 days in a typical year, longer than at 91% of the 219 California stations; it reaches 365 days one year in ten and falls short of 315 one year in ten. On average 4 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 33 days longer, to about February 9, and return around December 2. A 24°F night is unusual: 0% of winters had one.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F99% of yrs | Jan 6 | Jan 17 | Jan 28 | Feb 3 | Feb 9 | Feb 16 | Feb 21 | Feb 28 | Mar 6 |
| 32°F80% of yrs | Dec 19 | Dec 26 | Dec 31 | Jan 3 | Jan 7 | Jan 11 | Jan 17 | Jan 25 | Feb 1 |
| 28°F25% of yrs | too rare for a date | ||||||||
| 24°F0% of yrs | too rare for a date | ||||||||
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F99% of yrs | Nov 15 | Nov 21 | Nov 26 | Dec 1 | Dec 2 | Dec 5 | Dec 10 | Dec 15 | Dec 24 |
| 32°F80% of yrs | Dec 1 | Dec 5 | Dec 11 | Dec 16 | Dec 19 | Dec 23 | Dec 29 | Jan 3 | Jan 12 |
| 28°F25% of yrs | too rare for a date | ||||||||
| 24°F0% of yrs | too rare for a date | ||||||||
Freeze probabilities 1991–2020 at Concord Wwtp, 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 94595 →Compare Walnut Creek with another place →
Weather by month in Walnut Creek
August is the warmest month at Concord Wwtp, CA, averaging 88°F by day and 59°F at night; December is the coldest at 59°F and 41°F. From February to November the chance of a 32°F night stays under 10% each month.
Warmth for growing adds up to 4,672 growing degree days a year (base 50°F), more than at 53% of the 283 California stations. 39% of them (1,825) have built up by the end of June, and August adds the most, 729. Precipitation totals 17.9 inches a year, most in February (3.6") and least in July (0.0"); May to September bring 4% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 58 | 42 | 3.5 | 47% | 2 | 56 |
| Feb | 63 | 44 | 3.6 | 8% | <1 | 117 |
| Mar | 68 | 47 | 2.6 | 0% | 0 | 228 |
| Apr | 72 | 49 | 1.2 | 0% | 0 | 321 |
| May | 78 | 53 | 0.6 | 0% | 0 | 482 |
| Jun | 85 | 57 | 0.1 | 0% | 0 | 619 |
| Jul | 88 | 58 | 0.0 | 0% | 0 | 722 |
| Aug | 88 | 59 | 0.0 | 0% | 0 | 729 |
| Sep | 86 | 58 | 0.1 | 0% | 0 | 655 |
| Oct | 78 | 53 | 0.7 | 0% | 0 | 485 |
| Nov | 67 | 46 | 1.9 | 6% | <1 | 198 |
| Dec | 59 | 41 | 3.6 | 57% | 2 | 58 |
Monthly normals 1991–2020 at Concord Wwtp, CA (40 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, Mt Diablo Junction, CA, 8 miles east of Walnut Creek and 2,130 feet higher, has a last frost 60 days later (March 8), a first frost 3 days later (December 22), a season 64 days shorter.
When it snows in Walnut Creek, California
Measurable snow is rare here: only 0 of 19 winters from 1991 to 2020 recorded 0.1 inch or more at Concord Wwtp, CA, 7.2 miles away, so there is no typical first-snow date to plan around.
Where these figures come from
ZIP 94595 is 7 miles from Concord Wwtp, CA, which stands at 40 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 4 other ZIP codes share the station; its figures are presented in full for 94523 (Pleasant Hill). The 2023 USDA Plant Hardiness Zone Map lists ZIP 94595 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.