Planting zone for 91342 — Sylmar, CA
ZIP code 91342 (Sylmar, Los Angeles County) is in USDA zone 10a: the coldest winter night averages 30 to 35 °F.
Where ZIP 91342 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 Sylmar, 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 Burbank Glendale Pasadena Airport, CA — 9 miles away, elevation 742 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 91342 came on Jan 17 — 8 days earlier than the 1991–2020 average (Jan 25).
Jan 252026
Jan 17
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 Sylmar, CA
The soil mapped at the center of ZIP 91342 is Chilao family — gravelly loam, somewhat excessively drained.
Map unit: Chilao-Trigo, granitic substratum-Lodo families complex, 55 to 85 percent slopes.
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 91342; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.
Climate in Sylmar, CA
Average high and low, by month
Precipitation by month inches
NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Burbank Glendale Pasadena Airport, CA (9 mi away); precipitation: Pacoima Dam Fc33a-E, CA (within 1 mile). Daylight is calculated from latitude.
Nearby ZIP codes
1 of the 8 nearest ZIP codes are in a different zone — elevation and distance from water change winter lows quickly.
Questions about 91342
What planting zone is ZIP code 91342?
ZIP code 91342 (Sylmar, 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 91342 get?
About 18.6 inches of precipitation a year (NOAA 1991–2020 normals, Pacoima Dam Fc33a-E station).
How hot do summers get in Sylmar, CA?
The average high peaks at 89 °F in August, with about 54 days a year at 90 °F or more.
What kind of soil does 91342 have?
The USDA soil survey maps Chilao family at the center of ZIP 91342: gravelly loam, somewhat excessively drained, pH about 6.4 (slightly acidic).
Did spring come early in Sylmar, CA in 2026?
Spring leaf-out near 91342 came on Jan 17 in 2026, 8 days earlier than the 1991–2020 average (Jan 25), according to the USA National Phenology Network Spring Index.
What kind of onions grow in Sylmar, CA?
Intermediate onions: the longest day near 91342 is 14 h 27 min, so day-neutral types bulb best; long-day varieties may not bulb fully.
Did the zone for 91342 change?
Yes. The 2012 USDA map put 91342 in zone 9b; the 2023 map puts it in zone 10a. The newer map uses 1991–2020 data and more weather stations.