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

Planting zone for 92837 — Fullerton, CA

ZIP code 92837 (Fullerton, Orange County) is in USDA zone 10a: the coldest winter night averages 30 to 35 °F.

Where ZIP 92837 is

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 zone10b

Was 10b on the 2012 map — half a zone colder 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 Service

Loading the forecast for Fullerton, 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 Tustin Irvine Rch, CA — 17 miles away, elevation 236 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 92837 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 Fullerton, CA

The soil mapped at the center of ZIP 92837 is San Emigdio — fine sandy loam, well drained.

TextureFine sandy loamdrains and warms fast; dries out and needs more feeding
pH8.2alkaline; most vegetables like 6.0–7.0
DrainageWell drainednatural drainage class
Organic matter0.75%low — add compost
Hydrologic groupAwater soaks in fast
Farmland classPrime farmland if irrigatedUSDA classification

Map unit: San Emigdio fine sandy loam, 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 92837; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Fullerton, 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 54 mindaylight on December 21
Onions to growIntermediateday-neutral types bulb best; long-day varieties may not bulb fully
Precipitation11.9 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: 2.85 in precipitation 2.9 JanFebruary: 3.02 in precipitation 3.0 FebMarch: 1.74 in precipitation 1.7 MarApril: 0.59 in precipitation 0.6 AprMay: 0.30 in precipitation 0.3 MayJune: 0.08 in precipitation 0.1 JunJuly: 0.02 in precipitation 0.0 JulAugust: 0.02 in precipitation 0.0 AugSeptember: 0.14 in precipitation 0.1 SepOctober: 0.50 in precipitation 0.5 OctNovember: 0.74 in precipitation 0.7 NovDecember: 1.86 in precipitation 1.9 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Fullerton Municipal Airport, CA (within 1 mile); precipitation: Fullerton Municipal Airport, CA (within 1 mile). Daylight is calculated from latitude.

Nearby ZIP codes

5 of the 8 nearest ZIP codes are in a different zone — elevation and distance from water change winter lows quickly.

9283310a
Fullerton, CA · <1 mi
9280110b
Anaheim, CA · 2 mi
9285010b
Anaheim, CA · 2 mi
9283210b
Fullerton, CA · 2 mi
9062110a
Buena Park, CA · 2 mi
9280910a
Anaheim, CA · 2 mi
9283810b
Fullerton, CA · 2 mi
9280310b
Anaheim, CA · 2 mi

All 8 ZIP codes in Fullerton → · California planting zones →

Questions about 92837

What planting zone is ZIP code 92837?

ZIP code 92837 (Fullerton, 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 92837 get?

About 11.9 inches of precipitation a year (NOAA 1991–2020 normals, Fullerton Municipal Airport station).

How hot do summers get in Fullerton, 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 92837 have?

The USDA soil survey maps San Emigdio at the center of ZIP 92837: fine sandy loam, well drained, pH about 8.2 (alkaline).

Did spring come early in Fullerton, CA in 2026?

Spring leaf-out near 92837 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 Fullerton, CA?

Intermediate onions: the longest day near 92837 is 14 h 25 min, so day-neutral types bulb best; long-day varieties may not bulb fully.

Did the zone for 92837 change?

Yes. The 2012 USDA map put 92837 in zone 10b; the 2023 map puts it in zone 10a. The newer map uses 1991–2020 data and more weather stations.