Data: 2023 USDA zones (PRISM/OSU) · NOAA 1991–2020 normals · updated

Planting zone for 90242 — Downey, CA

ZIP code 90242 (Downey, Los Angeles County) is in USDA zone 10b: the coldest winter night averages 35 to 40 °F.

Where ZIP 90242 is

Outlined: the ZIP code area · tap the map for the zone at any spot · scroll or pinch to zoom

Not 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.

Zone10b35 to 40 °F
Coldest night1.7 to 4.4 °C
Last frostrare
First frostrare
2012 zone10b

Same zone as on the 2012 map. The zone is the one at the center of the ZIP code; hilly ZIPs can span two zones. What zone 10b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Downey, 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 San Gabriel Fire Dept, CA — 11 miles away, elevation 364 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 90242 came on Jan 17 — 4 days earlier than the 1991–2020 average (Jan 21).

JanFebMarAprMayJun

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 Downey, CA

The soil mapped at the center of ZIP 90242 is Hueneme — sandy loam, somewhat poorly drained. Much of the area is built over (urban land); this is the natural soil underneath.

TextureSandy loamdrains and warms fast; dries out and needs more feeding
pH7.2neutral; most vegetables like 6.0–7.0
DrainageSomewhat poorly drainedconsider raised beds
Organic matter1%low — add compost
Hydrologic groupBwater soaks in moderately
Farmland classPrime farmland if irrigated and drainedUSDA classification

Map unit: Urban land-Hueneme, drained-San Emigdio complex, 0 to 2 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 90242; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Downey, CA

Summer high83 °Faverage high, August
Winter low47 °Faverage low, January
Hot days23days a year at 90 °F or more
Freezing nights0nights a year at 32 °F or less
Growing degree days5,476base 50 °F — the season’s usable heat
Longest day14 h 25 mindaylight on June 21
Shortest day9 h 54 mindaylight on December 21
Onions to growIntermediateday-neutral types bulb best; long-day varieties may not bulb fully
Precipitation15.2 inper year, rain and melted snow

Average high and low, by month

40°50°60°70°80°90°January: average high 67 °F, low 47 °F 67°47° JanFebruary: average high 67 °F, low 48 °F 67°48° FebMarch: average high 69 °F, low 51 °F 69°51° MarApril: average high 71 °F, low 54 °F 71°54° AprMay: average high 73 °F, low 58 °F 73°58° MayJune: average high 76 °F, low 61 °F 76°61° JunJuly: average high 81 °F, low 65 °F 81°65° JulAugust: average high 83 °F, low 66 °F 83°66° AugSeptember: average high 82 °F, low 64 °F 82°64° SepOctober: average high 78 °F, low 59 °F 78°59° OctNovember: average high 73 °F, low 52 °F 73°52° NovDecember: average high 67 °F, low 47 °F 67°47° Dec

Precipitation by month inches

0″1″2″3″4″5″January: 3.02 in precipitation 3.0 JanFebruary: 4.64 in precipitation 4.6 FebMarch: 2.22 in precipitation 2.2 MarApril: 0.74 in precipitation 0.7 AprMay: 0.40 in precipitation 0.4 MayJune: 0.08 in precipitation 0.1 JunJuly: 0.03 in precipitation 0.0 JulAugust: 0.01 in precipitation 0.0 AugSeptember: 0.11 in precipitation 0.1 SepOctober: 0.41 in precipitation 0.4 OctNovember: 0.89 in precipitation 0.9 NovDecember: 2.63 in precipitation 2.6 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Long Beach Daugherty Field, CA (7 mi away); precipitation: Whittier 2.9 Wnw, CA (6 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 10b.

9023910b
Downey, CA · 1 mi
9024110b
Downey, CA · 1 mi
9072310b
Paramount, CA · 2 mi
9070610b
Bellflower, CA · 2 mi
9024010b
Downey, CA · 3 mi
9070710b
Bellflower, CA · 3 mi
9028010b
South Gate, CA · 3 mi
9065010b
Norwalk, CA · 3 mi

All 4 ZIP codes in Downey → · California planting zones →

Questions about 90242

What planting zone is ZIP code 90242?

ZIP code 90242 (Downey, CA) is in USDA hardiness zone 10b on the 2023 map: the coldest night of an average winter reaches 35 to 40 °F (1.7 to 4.4 °C).

How much rain and snow does 90242 get?

About 15.2 inches of precipitation a year (NOAA 1991–2020 normals, Whittier 2.9 Wnw station).

How hot do summers get in Downey, CA?

The average high peaks at 83 °F in August, with about 23 days a year at 90 °F or more.

What kind of soil does 90242 have?

The USDA soil survey maps Hueneme at the center of ZIP 90242: sandy loam, somewhat poorly drained, pH about 7.2 (neutral).

Did spring come early in Downey, CA in 2026?

Spring leaf-out near 90242 came on Jan 17 in 2026, 4 days earlier than the 1991–2020 average (Jan 21), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Downey, CA?

Intermediate onions: the longest day near 90242 is 14 h 25 min, so day-neutral types bulb best; long-day varieties may not bulb fully.