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

Planting zone for 93422 — Atascadero, CA

ZIP code 93422 (Atascadero, San Luis Obispo County) is in USDA zone 9a: the coldest winter night averages 20 to 25 °F.

Where ZIP 93422 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.

Zone9a20 to 25 °F
Coldest night−6.7 to −3.9 °C
Last frostrare
First frostrare
2012 zone9a

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 9a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Atascadero, 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 — 11 miles away, 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 93422 came on Jan 23 — 6 days earlier than the 1991–2020 average (Jan 29).

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 Atascadero, CA

The soil mapped at the center of ZIP 93422 is Millsholm — clay loam, well drained.

TextureClay loamholds water and nutrients; slow to drain and warm up
pH6.5neutral; most vegetables like 6.0–7.0
DrainageWell drainednatural drainage class
Organic matter2%moderate
Hydrologic groupDwater soaks in very slowly
Farmland classNot prime farmlandUSDA classification

Map unit: Millsholm-Dibble complex, 30 to 50 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 93422; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Atascadero, 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 45 mindaylight on December 21
Onions to growIntermediateday-neutral types bulb best; long-day varieties may not bulb fully
Precipitation31.6 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″2″4″6″8″January: 7.43 in precipitation 7.4 JanFebruary: 6.79 in precipitation 6.8 FebMarch: 5.25 in precipitation 5.3 MarApril: 1.82 in precipitation 1.8 AprMay: 0.67 in precipitation 0.7 MayJune: 0.16 in precipitation 0.2 JunJuly: 0.05 in precipitation 0.1 JulAugust: 0.01 in precipitation 0.0 AugSeptember: 0.12 in precipitation 0.1 SepOctober: 1.59 in precipitation 1.6 OctNovember: 2.54 in precipitation 2.5 NovDecember: 5.15 in precipitation 5.2 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Morro Bay Fire Dept, CA (11 mi away); precipitation: Santa Margarita Boost, CA (7 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

934239a
Atascadero, CA · 5 mi
934659a
Templeton, CA · 6 mi
934429b
Morro Bay, CA · 8 mi
934099b
San Luis Obispo, CA · 10 mi
9340810a
San Luis Obispo, CA · 10 mi
934079b
San Luis Obispo, CA · 11 mi
934109b
San Luis Obispo, CA · 11 mi
9344310a
Morro Bay, CA · 11 mi

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

Questions about 93422

What planting zone is ZIP code 93422?

ZIP code 93422 (Atascadero, CA) is in USDA hardiness zone 9a on the 2023 map: the coldest night of an average winter reaches 20 to 25 °F (−6.7 to −3.9 °C).

How much rain and snow does 93422 get?

About 31.6 inches of precipitation a year (NOAA 1991–2020 normals, Santa Margarita Boost station).

How hot do summers get in Atascadero, 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 93422 have?

The USDA soil survey maps Millsholm at the center of ZIP 93422: clay loam, well drained, pH about 6.5 (neutral).

Did spring come early in Atascadero, CA in 2026?

Spring leaf-out near 93422 came on Jan 23 in 2026, 6 days earlier than the 1991–2020 average (Jan 29), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Atascadero, CA?

Intermediate onions: the longest day near 93422 is 14 h 33 min, so day-neutral types bulb best; long-day varieties may not bulb fully.