Planting zone for 93423 — Atascadero, CA
ZIP code 93423 (Atascadero, San Luis Obispo County) is in USDA zone 9a: the coldest winter night averages 20 to 25 °F.
Where ZIP 93423 is
tap the map for the zone at any spot · scroll or pinch to zoomNot 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.
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 ServiceLoading 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 — 6 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 93423 came on Jan 20 — 7 days earlier than the 1991–2020 average (Jan 27).
Jan 272026
Jan 20
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 93423 is Cuesta family — cobbly loam, well drained.
Map unit: Cuesta-Henneke families complex, 15 to 60 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 93423; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.
Climate in Atascadero, CA
Average high and low, by month
Precipitation by month inches
NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Morro Bay Fire Dept, CA (6 mi away); precipitation: Morro Bay Fire Dept, CA (6 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.
All 2 ZIP codes in Atascadero → · California planting zones →
Questions about 93423
What planting zone is ZIP code 93423?
ZIP code 93423 (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 93423 get?
About 17 inches of precipitation a year (NOAA 1991–2020 normals, Morro Bay Fire Dept 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 93423 have?
The USDA soil survey maps Cuesta family at the center of ZIP 93423: cobbly loam, well drained, pH about 7.2 (neutral).
Did spring come early in Atascadero, CA in 2026?
Spring leaf-out near 93423 came on Jan 20 in 2026, 7 days earlier than the 1991–2020 average (Jan 27), according to the USA National Phenology Network Spring Index.
What kind of onions grow in Atascadero, CA?
Intermediate onions: the longest day near 93423 is 14 h 33 min, so day-neutral types bulb best; long-day varieties may not bulb fully.