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

Planting zone for 93443 — Morro Bay, CA

ZIP code 93443 (Morro Bay, San Luis Obispo County) is in USDA zone 10a: the coldest winter night averages 30 to 35 °F.

Where ZIP 93443 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 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 Morro Bay, 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 Morro Bay Fire Dept, CA — within 1 mile, elevation 118 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 93443 came on Jan 19 — 5 days earlier than the 1991–2020 average (Jan 24).

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 Morro Bay, CA

The soil mapped at the center of ZIP 93443 is Baywood — fine sand, somewhat excessively drained.

TextureFine sanddrains and warms fast; dries out and needs more feeding
pH6.2slightly acidic; most vegetables like 6.0–7.0
DrainageSomewhat excessively drainednatural drainage class
Organic matter2.5%moderate
Hydrologic groupAwater soaks in fast
Farmland classNot prime farmlandUSDA classification

Map unit: Baywood fine 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 93443; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Morro Bay, CA

Summer high73 °Faverage high, October
Winter low46 °Faverage low, January
Hot days1days a year at 90 °F or more
Freezing nights3nights a year at 32 °F or less
Growing degree days3,512base 50 °F — the season’s usable heat
Longest day14 h 33 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
Precipitation17 inper year, rain and melted snow

Average high and low, by month

40°50°60°70°80°January: average high 65 °F, low 46 °F 65°46° JanFebruary: average high 65 °F, low 48 °F 65°48° FebMarch: average high 66 °F, low 49 °F 66°49° MarApril: average high 67 °F, low 49 °F 67°49° AprMay: average high 67 °F, low 52 °F 67°52° MayJune: average high 66 °F, low 54 °F 66°54° JunJuly: average high 67 °F, low 57 °F 67°57° JulAugust: average high 70 °F, low 57 °F 70°57° AugSeptember: average high 72 °F, low 56 °F 72°56° SepOctober: average high 73 °F, low 54 °F 73°54° OctNovember: average high 69 °F, low 50 °F 69°50° NovDecember: average high 65 °F, low 46 °F 65°46° Dec

Precipitation by month inches

0″1″2″3″4″January: 3.64 in precipitation, 0.1 in snowfall 3.6 JanFebruary: 3.62 in precipitation 3.6 FebMarch: 3.19 in precipitation 3.2 MarApril: 0.99 in precipitation 1.0 AprMay: 0.42 in precipitation 0.4 MayJune: 0.20 in precipitation 0.2 JunJuly: 0.07 in precipitation 0.1 JulAugust: 0.02 in precipitation 0.0 AugSeptember: 0.09 in precipitation 0.1 SepOctober: 0.68 in precipitation 0.7 OctNovember: 1.33 in precipitation 1.3 NovDecember: 2.75 in precipitation 2.8 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Morro Bay Fire Dept, CA (within 1 mile); precipitation: Morro Bay Fire Dept, 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.

934429b
Morro Bay, CA · 4 mi
9341210a
Los Osos, CA · 4 mi
9340210a
Los Osos, CA · 5 mi
934239a
Atascadero, CA · 6 mi
934059b
San Luis Obispo, CA · 8 mi
9340810a
San Luis Obispo, CA · 8 mi
934099b
San Luis Obispo, CA · 9 mi
9343010a
Cayucos, CA · 10 mi

All 2 ZIP codes in Morro Bay → · California planting zones →

Questions about 93443

What planting zone is ZIP code 93443?

ZIP code 93443 (Morro Bay, 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 93443 get?

About 17 inches of precipitation a year (NOAA 1991–2020 normals, Morro Bay Fire Dept station).

How hot do summers get in Morro Bay, CA?

The average high peaks at 73 °F in October, with about 1 days a year at 90 °F or more.

What kind of soil does 93443 have?

The USDA soil survey maps Baywood at the center of ZIP 93443: fine sand, somewhat excessively drained, pH about 6.2 (slightly acidic).

Did spring come early in Morro Bay, CA in 2026?

Spring leaf-out near 93443 came on Jan 19 in 2026, 5 days earlier than the 1991–2020 average (Jan 24), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Morro Bay, CA?

Intermediate onions: the longest day near 93443 is 14 h 33 min, so day-neutral types bulb best; long-day varieties may not bulb fully.