USDA Hardiness Zone 10a
Frost Dates for 91326 — Porter Ranch, California
NOAA 1991–2020 normals from Northridge Cal State, CA (904 ft), 3 miles southeast.
Updated
Frost is not a yearly event in Porter Ranch: a night at or below 32°F came in 18% of the winters of 1991–2020 at Northridge Cal State, CA, and a 36°F night, cold enough for frost on exposed leaves, in 74%. There is no reliable "last frost date" here; most years have none.
- Winters with a freeze
- 18%
- Winters with 36°F
- 74%
- Coldest month low
- 46°F
- Hardiness zone
- 10a
32°F or below, 1991–2020
frost possible on leaves
average, December
30 to 35°F (-1.1 to 1.7°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 20 observed
NOAA normal
Frost risk by date in Porter Ranch
At Northridge Cal State, CA, 3 miles southeast of Porter Ranch, 18% of the winters of 1991–2020 had at least one night at or below 32°F, 3% reached 28°F. Nights of 36°F, enough for frost on exposed leaves, are more common (74% of winters) and, when they come, fall between about December 25 and January 22. January is the month most likely to bring one: a 10% chance in a given year. 62 of the 283 other California stations behind this site's ZIP pages freeze in fewer than half of winters too.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F74% of yrs | Dec 16 | Dec 28 | Jan 4 | Jan 12 | Jan 22 | Jan 31 | Feb 10 | Feb 20 | Mar 1 |
| 32°F18% of yrs | too rare for a date | ||||||||
| 28°F3% of yrs | too rare for a date | ||||||||
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F74% of yrs | Nov 30 | Dec 7 | Dec 13 | Dec 19 | Dec 25 | Dec 31 | Jan 6 | Jan 19 | Feb 4 |
| 32°F18% of yrs | too rare for a date | ||||||||
| 28°F3% of yrs | too rare for a date | ||||||||
Freeze probabilities 1991–2020 at Northridge Cal State, 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 91326 →Compare Porter Ranch with another place →
Weather by month in Porter Ranch
August is the warmest month at Northridge Cal State, CA, averaging 92°F by day and 64°F at night; December is the coldest at 67°F and 46°F. From February to December the chance of a 32°F night stays under 10% each month.
Warmth for growing adds up to 5,956 growing degree days a year (base 50°F), more than at 90% of the 283 California stations. 39% of them (2,327) have built up by the end of June, and August adds the most, 870. Precipitation totals 14.7 inches a year, most in February (3.9") 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 | 67 | 47 | 3.4 | 10% | <1 | 233 |
| Feb | 68 | 47 | 3.9 | 0% | 0 | 213 |
| Mar | 71 | 49 | 2.4 | 1% | <1 | 317 |
| Apr | 75 | 52 | 0.7 | 0% | 0 | 395 |
| May | 78 | 56 | 0.4 | 0% | 0 | 518 |
| Jun | 84 | 60 | 0.1 | 0% | 0 | 651 |
| Jul | 90 | 64 | 0.0 | 0% | 0 | 834 |
| Aug | 92 | 64 | 0.0 | 0% | 0 | 870 |
| Sep | 89 | 62 | 0.1 | 0% | 0 | 768 |
| Oct | 82 | 56 | 0.6 | 0% | 0 | 583 |
| Nov | 74 | 50 | 0.8 | 0% | 0 | 368 |
| Dec | 67 | 46 | 2.3 | 8% | <1 | 207 |
Monthly normals 1991–2020 at Northridge Cal State, CA (904 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, Van Nuys Airport, CA, 6 miles southeast of Porter Ranch, has a 32°F night in 22% of winters against 18% here, and a coolest-month low 1°F colder (45°F).
When it snows in Porter Ranch, California
Measurable snow is rare here: only 0 of 20 winters from 1991 to 2020 recorded 0.1 inch or more at Woodland Hills Pierce College, CA, 6.7 miles away, so there is no typical first-snow date to plan around.
Where these figures come from
ZIP 91326 is 3 miles from Northridge Cal State, CA, which stands at 904 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 7 other ZIP codes share the station; its figures are presented in full for 91342 (Sylmar). The 2023 USDA Plant Hardiness Zone Map lists ZIP 91326 in zone 10a, the band where the coldest night of the year averaged 30 to 35°F (-1.1 to 1.7°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.