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

Planting zone for 91748 — Rowland Heights, CA

ZIP code 91748 (Rowland Heights, Los Angeles County) is in USDA zone 10a: the coldest winter night averages 30 to 35 °F.

Where ZIP 91748 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.

Zone10a30 to 35 °F
Coldest night−1.1 to 1.7 °C
Last frostrare
First frostrare
2012 zone10a

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 10a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Rowland Heights, 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 Pomona/Fairplex, CA — 11 miles away, elevation 1,001 ft) the median growing season is 354 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 91748 came on Jan 16 — 5 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 Rowland Heights, CA

The soil mapped at the center of ZIP 91748 is Arbolado — clay loam, well drained. Much of the area is built over (urban land); this is the natural soil underneath.

TextureClay loamholds water and nutrients; slow to drain and warm up
pH7.2neutral; most vegetables like 6.0–7.0
DrainageWell drainednatural drainage class
Organic matter2.5%moderate
Hydrologic groupCwater soaks in slowly
Farmland classPrime farmland if irrigatedUSDA classification

Map unit: Urban land-Sorrento-Arbolado complex, 2 to 9 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 91748; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Rowland Heights, CA

Summer high87 °Faverage high, August
Winter low46 °Faverage low, January
Hot days39days a year at 90 °F or more
Freezing nights0nights a year at 32 °F or less
Growing degree days5,940base 50 °F — the season’s usable heat
Longest day14 h 25 mindaylight on June 21
Shortest day9 h 53 mindaylight on December 21
Onions to growIntermediateday-neutral types bulb best; long-day varieties may not bulb fully
Precipitation16.3 inper year, rain and melted snow

Average high and low, by month

40°50°60°70°80°90°100°January: average high 69 °F, low 46 °F 69°46° JanFebruary: average high 69 °F, low 48 °F 69°48° FebMarch: average high 71 °F, low 52 °F 71°52° MarApril: average high 74 °F, low 54 °F 74°54° AprMay: average high 76 °F, low 58 °F 76°58° MayJune: average high 79 °F, low 63 °F 79°63° JunJuly: average high 84 °F, low 66 °F 84°66° JulAugust: average high 87 °F, low 66 °F 87°66° AugSeptember: average high 85 °F, low 65 °F 85°65° SepOctober: average high 80 °F, low 58 °F 80°58° OctNovember: average high 74 °F, low 51 °F 74°51° NovDecember: average high 68 °F, low 46 °F 68°46° Dec

Precipitation by month inches

0″1″2″3″4″January: 3.30 in precipitation 3.3 JanFebruary: 3.88 in precipitation 3.9 FebMarch: 2.79 in precipitation 2.8 MarApril: 0.78 in precipitation 0.8 AprMay: 0.43 in precipitation 0.4 MayJune: 0.12 in precipitation 0.1 JunJuly: 0.07 in precipitation 0.1 JulAugust: 0.03 in precipitation 0.0 AugSeptember: 0.12 in precipitation 0.1 SepOctober: 0.85 in precipitation 0.8 OctNovember: 1.00 in precipitation 1.0 NovDecember: 2.94 in precipitation 2.9 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Fullerton Municipal Airport, CA (9 mi away); precipitation: Diamond Bar 1.9 Nne, CA (7 mi away). 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.

9179210a
West Covina, CA · 3 mi
9178810a
Walnut, CA · 4 mi
9063110a
La Habra, CA · 4 mi
9178910a
Walnut, CA · 4 mi
9063310a
La Habra, CA · 4 mi
9174710b
La Puente, CA · 4 mi
9174910a
La Puente, CA · 4 mi
9174410a
La Puente, CA · 4 mi

California planting zones →

Questions about 91748

What planting zone is ZIP code 91748?

ZIP code 91748 (Rowland Heights, 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 91748 get?

About 16.3 inches of precipitation a year (NOAA 1991–2020 normals, Diamond Bar 1.9 Nne station).

How hot do summers get in Rowland Heights, CA?

The average high peaks at 87 °F in August, with about 39 days a year at 90 °F or more.

What kind of soil does 91748 have?

The USDA soil survey maps Arbolado at the center of ZIP 91748: clay loam, well drained, pH about 7.2 (neutral).

Did spring come early in Rowland Heights, CA in 2026?

Spring leaf-out near 91748 came on Jan 16 in 2026, 5 days earlier than the 1991–2020 average (Jan 21), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Rowland Heights, CA?

Intermediate onions: the longest day near 91748 is 14 h 25 min, so day-neutral types bulb best; long-day varieties may not bulb fully.