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

Planting zone for 92178 — Coronado, CA

ZIP code 92178 (Coronado, San Diego County) is in USDA zone 10b: the coldest winter night averages 35 to 40 °F.

Where ZIP 92178 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.

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 Coronado, 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 Diego Brown Field, CA — 14 miles away, elevation 515 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 92178 came on Jan 19 — about the same time as 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 Coronado, CA

The soil mapped at the center of ZIP 92178 is Marina — loamy coarse sand, somewhat excessively drained.

TextureLoamy coarse sanddrains and warms fast; dries out and needs more feeding
pH6.5neutral; most vegetables like 6.0–7.0
DrainageSomewhat excessively drainednatural drainage class
Organic matter0.75%low — add compost
Hydrologic groupBwater soaks in moderately
Farmland classPrime farmland if irrigatedUSDA classification

Map unit: Marina loamy coarse sand, 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 92178; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Coronado, CA

Summer high77 °Faverage high, August
Winter low49 °Faverage low, January
Hot days4days a year at 90 °F or more
Freezing nights0nights a year at 32 °F or less
Growing degree days5,094base 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
Precipitation9.3 inper year, rain and melted snow

Average high and low, by month

40°50°60°70°80°90°January: average high 66 °F, low 49 °F 66°49° JanFebruary: average high 66 °F, low 51 °F 66°51° FebMarch: average high 67 °F, low 53 °F 67°53° MarApril: average high 68 °F, low 55 °F 68°55° AprMay: average high 69 °F, low 59 °F 69°59° MayJune: average high 71 °F, low 62 °F 71°62° JunJuly: average high 74 °F, low 65 °F 74°65° JulAugust: average high 77 °F, low 67 °F 77°67° AugSeptember: average high 77 °F, low 65 °F 77°65° SepOctober: average high 75 °F, low 60 °F 75°60° OctNovember: average high 71 °F, low 54 °F 71°54° NovDecember: average high 66 °F, low 49 °F 66°49° Dec

Precipitation by month inches

0″1″2″January: 1.67 in precipitation 1.7 JanFebruary: 1.94 in precipitation 1.9 FebMarch: 1.45 in precipitation 1.4 MarApril: 0.64 in precipitation 0.6 AprMay: 0.45 in precipitation 0.5 MayJune: 0.06 in precipitation 0.1 JunJuly: 0.09 in precipitation 0.1 JulAugust: 0.02 in precipitation 0.0 AugSeptember: 0.16 in precipitation 0.2 SepOctober: 0.59 in precipitation 0.6 OctNovember: 0.78 in precipitation 0.8 NovDecember: 1.48 in precipitation 1.5 Dec

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

Nearby ZIP codes

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

9213511a
San Diego, CA · <1 mi
9211810b
Coronado, CA · 2 mi
9213211a
San Diego, CA · 2 mi
9210111a
San Diego, CA · 2 mi
9215510b
San Diego, CA · 2 mi
9211210b
San Diego, CA · 3 mi
9213811a
San Diego, CA · 3 mi
9214210b
San Diego, CA · 3 mi

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

Questions about 92178

What planting zone is ZIP code 92178?

ZIP code 92178 (Coronado, 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 92178 get?

About 9.3 inches of precipitation a year (NOAA 1991–2020 normals, North Island NAS station).

How hot do summers get in Coronado, CA?

The average high peaks at 77 °F in August, with about 4 days a year at 90 °F or more.

What kind of soil does 92178 have?

The USDA soil survey maps Marina at the center of ZIP 92178: loamy coarse sand, somewhat excessively drained, pH about 6.5 (neutral).

Did spring come early in Coronado, CA in 2026?

Spring leaf-out near 92178 came on Jan 19 in 2026, about the same as the 1991–2020 average (Jan 21), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Coronado, CA?

Intermediate onions: the longest day near 92178 is 14 h 18 min, so day-neutral types bulb best; long-day varieties may not bulb fully.