Planting zone for 91321 — Newhall, CA
ZIP code 91321 (Newhall, Los Angeles County) is in USDA zone 10a: the coldest winter night averages 30 to 35 °F.
Where ZIP 91321 is
Outlined: the ZIP code area · tap the map for the zone at any spot · scroll or pinch to zoomNot the official USDA Plant Hardiness Zone Map. Zones come from the 2023 USDA hardiness-zone data by the PRISM Group, Oregon State University; we re-mapped and recolored them. The official map is at planthardiness.ars.usda.gov.
Was 9b on the 2012 map — half a zone warmer now. The zone is the one at the center of the ZIP code; hilly ZIPs can span two zones. What zone 10a means →
Frost forecast — next 7 nights
live from the National Weather ServiceLoading the forecast for Newhall, CA…
Forecast data: National Weather Service (api.weather.gov), public domain. This is not a warning service — for official frost and freeze warnings see weather.gov.
Frost dates
A 32 °F frost doesn't happen here in most winters. At the nearest station (NOAA station Newhall 5nw, CA — 6 miles away, elevation 1,765 ft) the median growing season is 365 days. When frost does come, it is a midwinter night or two; cover tender plants when a freeze is forecast.
Frost data: NOAA NCEI U.S. Climate Normals 1991–2020.
When spring arrived in 2026
In 2026, spring leaf-out near 91321 came on Jan 18 — 6 days earlier than the 1991–2020 average (Jan 24).
Jan 242026
Jan 18
The Spring Index marks the day when accumulated warmth is enough for lilac and honeysuckle to leaf out — a widely used signal that the growing season has started. Source: USA National Phenology Network, www.usanpn.org — Spring Indices, first leaf, 2026 (data as of 2026-09-08) and 30-year average 1991–2020 (CC BY 4.0).
Soil in Newhall, CA
The soil mapped at the center of ZIP 91321 is Saugus — loam, well drained.
Map unit: Saugus loam, 30 to 50 percent slopes, eroded.
Soil Survey Staff, Natural Resources Conservation Service, USDA. Soil Survey Geographic (SSURGO) Database, via Soil Data Access, accessed 2026-10-29. The soil at the center point of ZIP 91321; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.
Climate in Newhall, CA
Average high and low, by month
Precipitation by month inches
NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Newhall 5nw, CA (6 mi away); precipitation: Pacoima Dam Fc33a-E, CA (6 mi away). Daylight is calculated from latitude.
Nearby ZIP codes
All 8 nearest ZIP codes share zone 10a.
Questions about 91321
What planting zone is ZIP code 91321?
ZIP code 91321 (Newhall, CA) is in USDA hardiness zone 10a on the 2023 map: the coldest night of an average winter reaches 30 to 35 °F (−1.1 to 1.7 °C).
How much rain and snow does 91321 get?
About 18.6 inches of precipitation a year (NOAA 1991–2020 normals, Pacoima Dam Fc33a-E station).
How hot do summers get in Newhall, CA?
The average high peaks at 96 °F in August, with about 87 days a year at 90 °F or more.
What kind of soil does 91321 have?
The USDA soil survey maps Saugus at the center of ZIP 91321: loam, well drained, pH about 6.7 (neutral).
Did spring come early in Newhall, CA in 2026?
Spring leaf-out near 91321 came on Jan 18 in 2026, 6 days earlier than the 1991–2020 average (Jan 24), according to the USA National Phenology Network Spring Index.
What kind of onions grow in Newhall, CA?
Intermediate onions: the longest day near 91321 is 14 h 27 min, so day-neutral types bulb best; long-day varieties may not bulb fully.
Did the zone for 91321 change?
Yes. The 2012 USDA map put 91321 in zone 9b; the 2023 map puts it in zone 10a. The newer map uses 1991–2020 data and more weather stations.