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

Planting zone for 92231 — Calexico, CA

ZIP code 92231 (Calexico, Imperial County) is in USDA zone 10a: the coldest winter night averages 30 to 35 °F.

Where ZIP 92231 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 Calexico, 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 El Centro 2 Ssw, CA — 6 miles away, elevation -30 ft) the median growing season is 363 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 92231 came on Jan 18 — 4 days earlier than the 1991–2020 average (Jan 22).

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 Calexico, CA

The soil mapped at the center of ZIP 92231 is Imperial — silty clay, moderately well drained.

TextureSilty clayholds water and nutrients; slow to drain and warm up
pH8.2alkaline; most vegetables like 6.0–7.0
DrainageModerately well drainednatural drainage class
Organic matter0.5%low — add compost
Hydrologic groupCwater soaks in slowly
Farmland classPrime farmland if irrigated and reclaimed of excess salts and sodiumUSDA classification

Map unit: Imperial silty clay, wet.

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 92231; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Calexico, CA

Summer high107 °Faverage high, July
Winter low43 °Faverage low, January
Hot days180days a year at 90 °F or more
Freezing nights1nights a year at 32 °F or less
Growing degree days8,902base 50 °F — the season’s usable heat
Longest day14 h 18 mindaylight on June 21
Shortest day10 h 00 mindaylight on December 21
Onions to growIntermediateday-neutral types bulb best; long-day varieties may not bulb fully
Precipitation2.5 inper year, rain and melted snow

Average high and low, by month

30°40°50°60°70°80°90°100°110°120°32 °FJanuary: average high 71 °F, low 43 °F 71°43° JanFebruary: average high 74 °F, low 47 °F 74°47° FebMarch: average high 80 °F, low 52 °F 80°52° MarApril: average high 86 °F, low 57 °F 86°57° AprMay: average high 94 °F, low 63 °F 94°63° MayJune: average high 103 °F, low 71 °F 103°71° JunJuly: average high 107 °F, low 78 °F 107°78° JulAugust: average high 107 °F, low 79 °F 107°79° AugSeptember: average high 102 °F, low 73 °F 102°73° SepOctober: average high 92 °F, low 62 °F 92°62° OctNovember: average high 79 °F, low 51 °F 79°51° NovDecember: average high 70 °F, low 43 °F 70°43° Dec

Precipitation by month inches

0″1″January: 0.39 in precipitation 0.4 JanFebruary: 0.43 in precipitation 0.4 FebMarch: 0.29 in precipitation 0.3 MarApril: 0.07 in precipitation 0.1 AprMay: 0.04 in precipitation 0.0 MayJune: 0.00 in precipitation 0.0 JunJuly: 0.08 in precipitation 0.1 JulAugust: 0.23 in precipitation 0.2 AugSeptember: 0.25 in precipitation 0.3 SepOctober: 0.21 in precipitation 0.2 OctNovember: 0.17 in precipitation 0.2 NovDecember: 0.37 in precipitation 0.4 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: El Centro 2 Ssw, CA (6 mi away); precipitation: El Centro 2 Ssw, CA (6 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 10a.

9223210a
Calexico, CA · 4 mi
9224910a
Heber, CA · 5 mi
9224310a
El Centro, CA · 6 mi
9224410a
El Centro, CA · 11 mi
9227310a
Seeley, CA · 11 mi
9225110a
Imperial, CA · 15 mi
9225910a
Ocotillo, CA · 22 mi
9222710a
Brawley, CA · 25 mi

All 2 ZIP codes in Calexico → · California planting zones →

Questions about 92231

What planting zone is ZIP code 92231?

ZIP code 92231 (Calexico, 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 92231 get?

About 2.5 inches of precipitation a year (NOAA 1991–2020 normals, El Centro 2 Ssw station).

How hot do summers get in Calexico, CA?

The average high peaks at 107 °F in July, with about 180 days a year at 90 °F or more.

What kind of soil does 92231 have?

The USDA soil survey maps Imperial at the center of ZIP 92231: silty clay, moderately well drained, pH about 8.2 (alkaline).

Did spring come early in Calexico, CA in 2026?

Spring leaf-out near 92231 came on Jan 18 in 2026, 4 days earlier than the 1991–2020 average (Jan 22), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Calexico, CA?

Intermediate onions: the longest day near 92231 is 14 h 18 min, so day-neutral types bulb best; long-day varieties may not bulb fully.