Data: 2023 USDA zones (PRISM/OSU) · NOAA 1991–2020 normals · updated Oct 29, 2026

Planting zone for San Luis Obispo, CA

San Luis Obispo, CA is in USDA zones 9b to 10a across its 8 ZIP codes.

San Luis Obispo on the zone map

Outlined: its 6 ZIP code areas · 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.

Zones9b–10a25 to 35 °F

ZIP codes8

Last frostrare

First frostrare

Growing seasonall year

9b 5 ZIPs 10a 3 ZIPs

Frost forecast — next 7 nights

live from the National Weather Service

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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 Luis Obispo Poly, CA, elevation 308 ft) the median growing season is 349 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 93407 came on Jan 19 — 6 days earlier than the 1991–2020 average (Jan 25).

average
Jan 252026
Jan 19

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 Luis Obispo, CA

The soil mapped at the center of ZIP 93407 is Salinas — silty clay loam, well drained.

TextureSilty clay loamholds water and nutrients; slow to drain and warm up

pH8.0alkaline; 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: Salinas silty clay loam, 0 to 2 percent slopes, MLRA 14.

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 93407; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in San Luis Obispo, CA

Summer high80 °Faverage high, August

Winter low44 °Faverage low, January

Hot days19days a year at 90 °F or more

Freezing nights3nights a year at 32 °F or less

Growing degree days3,929base 50 °F — the season’s usable heat

Longest day14 h 32 mindaylight on June 21

Shortest day9 h 46 mindaylight on December 21

Onions to growIntermediateday-neutral types bulb best; long-day varieties may not bulb fully

Precipitation22.4 inper year, rain and melted snow

Average high and low, by month

Precipitation by month inches

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: San Luis Obispo Poly, CA (within 1 mile); precipitation: San Luis Obispo Poly, CA (within 1 mile). Daylight is calculated from latitude.