Planting zone for 94548 — Knightsen, CA
ZIP code 94548 (Knightsen, Contra Costa County) is in USDA zone 9b: the coldest winter night averages 25 to 30 °F.
Where ZIP 94548 is
Outlined: the ZIP code area · 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 9b means →
Frost forecast — next 7 nights
live from the National Weather ServiceLoading the forecast for Knightsen, 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 Antioch Pumping Plt #3, CA — 6 miles away, elevation 59 ft) the median growing season is 343 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 94548 came on Jan 31 — about the same time as the 1991–2020 average (Jan 31).
Jan 312026
Jan 31
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 Knightsen, CA
The soil mapped at the center of ZIP 94548 is Marcuse — clay, poorly drained.
Map unit: Marcuse clay, moderately saline, sodic, partially drained 0 to 2 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 94548; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.
Climate in Knightsen, CA
Average high and low, by month
Precipitation by month inches
NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Antioch Pumping Plt #3, CA (6 mi away); precipitation: Antioch Pumping Plt #3, CA (6 mi away). Daylight is calculated from latitude.
Nearby ZIP codes
All 8 nearest ZIP codes share zone 9b.
Questions about 94548
What planting zone is ZIP code 94548?
ZIP code 94548 (Knightsen, CA) is in USDA hardiness zone 9b on the 2023 map: the coldest night of an average winter reaches 25 to 30 °F (−3.9 to −1.1 °C).
How much rain and snow does 94548 get?
About 12.6 inches of precipitation a year (NOAA 1991–2020 normals, Antioch Pumping Plt #3 station).
How hot do summers get in Knightsen, CA?
The average high peaks at 91 °F in July, with about 64 days a year at 90 °F or more.
What kind of soil does 94548 have?
The USDA soil survey maps Marcuse at the center of ZIP 94548: clay, poorly drained, pH about 8.2 (alkaline).
Did spring come early in Knightsen, CA in 2026?
Spring leaf-out near 94548 came on Jan 31 in 2026, about the same as the 1991–2020 average (Jan 31), according to the USA National Phenology Network Spring Index.
What kind of onions grow in Knightsen, CA?
Intermediate onions: the longest day near 94548 is 14 h 48 min, so day-neutral types bulb best; long-day varieties may not bulb fully.