Planting zone for 94030 — Millbrae, CA
ZIP code 94030 (Millbrae, San Mateo County) is in USDA zone 10a: the coldest winter night averages 30 to 35 °F.
Where ZIP 94030 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 10a means →
Frost forecast — next 7 nights
live from the National Weather ServiceLoading the forecast for Millbrae, 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 San Francisco Intl Airport, CA — 2 miles away, elevation 7 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 94030 came on Jan 26 — about the same time as the 1991–2020 average (Jan 27).
Jan 272026
Jan 26
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 Millbrae, CA
The soil mapped at the center of ZIP 94030 is Orthents — variable, well drained.
Map unit: Orthents, cut and fill, 0 to 15 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 94030; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.
Climate in Millbrae, CA
Average high and low, by month
Precipitation by month inches
NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: San Francisco Intl Airport, CA (2 mi away); precipitation: San Francisco Intl Airport, CA (2 mi away). Daylight is calculated from latitude.
Nearby ZIP codes
1 of the 8 nearest ZIP codes are in a different zone — elevation and distance from water change winter lows quickly.
Questions about 94030
What planting zone is ZIP code 94030?
ZIP code 94030 (Millbrae, 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 94030 get?
About 19.6 inches of precipitation a year (NOAA 1991–2020 normals, San Francisco Intl Airport station).
How hot do summers get in Millbrae, CA?
The average high peaks at 75 °F in September, with about 4 days a year at 90 °F or more.
What kind of soil does 94030 have?
The USDA soil survey maps Orthents at the center of ZIP 94030: variable, well drained.
Did spring come early in Millbrae, CA in 2026?
Spring leaf-out near 94030 came on Jan 26 in 2026, about the same as the 1991–2020 average (Jan 27), according to the USA National Phenology Network Spring Index.
What kind of onions grow in Millbrae, CA?
Intermediate onions: the longest day near 94030 is 14 h 46 min, so day-neutral types bulb best; long-day varieties may not bulb fully.