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

Planting zone for 92173 — San Ysidro, CA

ZIP code 92173 (San Ysidro, San Diego County) is in USDA zone 10b: the coldest winter night averages 35 to 40 °F.

Where ZIP 92173 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 San Ysidro, 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 — 4 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 92173 came on Jan 18 — 3 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 San Ysidro, CA

The soil mapped at the center of ZIP 92173 is Huerhuero — loam, moderately well drained.

TextureLoama good balance for most vegetables
pH5.6moderately acidic; most vegetables like 6.0–7.0
DrainageModerately well drainednatural drainage class
Organic matter1.5%low — add compost
Hydrologic groupDwater soaks in very slowly
Farmland classNot prime farmlandUSDA classification

Map unit: Huerhuero-Urban land 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 92173; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in San Ysidro, CA

Summer high75 °Faverage high, August
Winter low46 °Faverage low, December
Hot days2days a year at 90 °F or more
Freezing nights0nights a year at 32 °F or less
Growing degree days4,519base 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 growShort-daysummer days stay under about 14 h 20 min, so long-day varieties won’t bulb
Precipitation10.1 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 65 °F, low 48 °F 65°48° FebMarch: average high 66 °F, low 51 °F 66°51° MarApril: average high 67 °F, low 53 °F 67°53° AprMay: average high 68 °F, low 57 °F 68°57° MayJune: average high 70 °F, low 60 °F 70°60° JunJuly: average high 73 °F, low 64 °F 73°64° JulAugust: average high 75 °F, low 65 °F 75°65° AugSeptember: average high 75 °F, low 62 °F 75°62° SepOctober: average high 73 °F, low 56 °F 73°56° OctNovember: average high 70 °F, low 50 °F 70°50° NovDecember: average high 66 °F, low 46 °F 66°46° Dec

Precipitation by month inches

0″1″2″3″January: 1.99 in precipitation 2.0 JanFebruary: 2.30 in precipitation 2.3 FebMarch: 1.58 in precipitation 1.6 MarApril: 0.71 in precipitation 0.7 AprMay: 0.32 in precipitation 0.3 MayJune: 0.08 in precipitation 0.1 JunJuly: 0.08 in precipitation 0.1 JulAugust: 0.03 in precipitation 0.0 AugSeptember: 0.14 in precipitation 0.1 SepOctober: 0.49 in precipitation 0.5 OctNovember: 0.81 in precipitation 0.8 NovDecember: 1.52 in precipitation 1.5 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Imperial Beach Ream Field NAS, CA (4 mi away); precipitation: Chula Vista 3.1se, CA (3 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 10b.

9191110b
Chula Vista, CA · 4 mi
9193210b
Imperial Beach, CA · 4 mi
9193310b
Imperial Beach, CA · 4 mi
9215410b
San Diego, CA · 5 mi
9191010b
Chula Vista, CA · 6 mi
9191310b
Chula Vista, CA · 6 mi
9190910b
Chula Vista, CA · 6 mi
9191210b
Chula Vista, CA · 6 mi

All 2 ZIP codes in San Ysidro → · California planting zones →

Questions about 92173

What planting zone is ZIP code 92173?

ZIP code 92173 (San Ysidro, 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 92173 get?

About 10.1 inches of precipitation a year (NOAA 1991–2020 normals, Chula Vista 3.1se station).

How hot do summers get in San Ysidro, CA?

The average high peaks at 75 °F in August, with about 2 days a year at 90 °F or more.

What kind of soil does 92173 have?

The USDA soil survey maps Huerhuero at the center of ZIP 92173: loam, moderately well drained, pH about 5.6 (moderately acidic).

Did spring come early in San Ysidro, CA in 2026?

Spring leaf-out near 92173 came on Jan 18 in 2026, 3 days earlier than the 1991–2020 average (Jan 21), according to the USA National Phenology Network Spring Index.

What kind of onions grow in San Ysidro, CA?

Short-day onions: the longest day near 92173 is 14 h 18 min, so summer days stay under about 14 h 20 min, so long-day varieties won’t bulb.