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

Planting zone for 94583 — San Ramon, CA

ZIP code 94583 (San Ramon, Contra Costa County) is in USDA zone 9b: the coldest winter night averages 25 to 30 °F. The median last spring frost is March 8 and the first fall frost December 22.

Where ZIP 94583 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.

Zone9b25 to 30 °F
Coldest night−3.9 to −1.1 °C
Last frostMar 8
First frostDec 22
2012 zone9b

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 Service

Loading the forecast for San Ramon, 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 in San Ramon, CA

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMarch 8median — 50% chance of a later frost
Safe for tender plantsApril 15only 10% chance of frost after
First fall frostDecember 22median — 10% chance by Nov 23
Growing season282 daysfrost-free, median

A hard freeze (28 °F) usually ends around February 8 and returns around January 16.

From the NOAA station Mt Diablo Junction, CA — 8 miles away, elevation 2,169 ft. NOAA NCEI U.S. Climate Normals 1991–2020, 32 °F threshold. Low spots and valleys can freeze later in spring than the station.

When to plant vegetables in 94583

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Jan 25 – Feb 8
SpinachSow outdoors · Jan 25 – Feb 15
Broccoli, cabbageStart indoors · Dec 28 – Jan 11
Broccoli, cabbageTransplant · Feb 15 – Mar 1
Onion setsPlant outdoors · Feb 8 – Feb 22
PotatoesPlant outdoors · Feb 15 – Mar 1
LettuceSow outdoors · Feb 8 – Feb 22
Carrots, beetsSow outdoors · Feb 15 – Mar 1
TomatoesStart indoors · Jan 11 – Jan 25
TomatoesTransplant · Mar 15 – Mar 29
Peppers, eggplantStart indoors · Dec 28 – Jan 11
Peppers, eggplantTransplant · Mar 22 – Apr 5
BeansSow outdoors · Mar 15 – Mar 29
Sweet cornSow outdoors · Mar 15 – Mar 29
Cucumbers, squashSow outdoors · Mar 15 – Mar 29
Fall lettuce, spinachSow outdoors · Oct 27 – Nov 10
GarlicPlant cloves · Dec 8 – Jan 12
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Mar 8) and first fall frost (Dec 22) with the rules of thumb U.S. extension services publish. Cool-season crops take a light frost; warm-season crops do best once the soil is above about 60 °F.

When spring arrived in 2026

In 2026, spring leaf-out near 94583 came on Jan 27 — 4 days earlier than the 1991–2020 average (Jan 31).

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 San Ramon, CA

The soil mapped at the center of ZIP 94583 is Botella — clay loam, moderately well drained.

TextureClay loamholds water and nutrients; slow to drain and warm up
pH6.0slightly acidic; most vegetables like 6.0–7.0
DrainageModerately well drainednatural drainage class
Organic matter4%moderate
Hydrologic groupCwater soaks in slowly
Farmland classPrime farmland if irrigatedUSDA classification

Map unit: Botella clay loam, 0 to 2 percent slopes, MLRA 14.

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 94583; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in San Ramon, CA

Summer high83 °Faverage high, July
Winter low41 °Faverage low, December
Hot days27days a year at 90 °F or more
Freezing nights19nights a year at 32 °F or less
Growing degree days3,645base 50 °F — the season’s usable heat
Longest day14 h 47 mindaylight on June 21
Shortest day9 h 33 mindaylight on December 21
Onions to growIntermediateday-neutral types bulb best; long-day varieties may not bulb fully
Precipitation21.8 inper year, rain and melted snow

Average high and low, by month

30°40°50°60°70°80°90°32 °FJanuary: average high 54 °F, low 42 °F 54°42° JanFebruary: average high 55 °F, low 42 °F 55°42° FebMarch: average high 58 °F, low 43 °F 58°43° MarApril: average high 62 °F, low 44 °F 62°44° AprMay: average high 68 °F, low 49 °F 68°49° MayJune: average high 76 °F, low 55 °F 76°55° JunJuly: average high 83 °F, low 62 °F 83°62° JulAugust: average high 83 °F, low 61 °F 83°61° AugSeptember: average high 80 °F, low 60 °F 80°60° SepOctober: average high 72 °F, low 54 °F 72°54° OctNovember: average high 60 °F, low 46 °F 60°46° NovDecember: average high 53 °F, low 41 °F 53°41° Dec

Precipitation by month inches

0″1″2″3″4″5″January: 3.97 in precipitation 4.0 JanFebruary: 3.94 in precipitation 3.9 FebMarch: 3.19 in precipitation 3.2 MarApril: 1.76 in precipitation 1.8 AprMay: 0.75 in precipitation 0.8 MayJune: 0.24 in precipitation 0.2 JunJuly: 0.01 in precipitation 0.0 JulAugust: 0.06 in precipitation 0.1 AugSeptember: 0.17 in precipitation 0.2 SepOctober: 1.04 in precipitation 1.0 OctNovember: 2.17 in precipitation 2.2 NovDecember: 4.46 in precipitation 4.5 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Mt Diablo Junction, CA (8 mi away); precipitation: Castro Valley 0.4 Nne, CA (6 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

All 8 nearest ZIP codes share zone 9b.

945709b
Moraga, CA · 2 mi
945269b
Danville, CA · 3 mi
945829b
San Ramon, CA · 4 mi
945529b
Castro Valley, CA · 5 mi
945289b
Diablo, CA · 5 mi
945069b
Danville, CA · 5 mi
945079b
Alamo, CA · 6 mi
945689b
Dublin, CA · 6 mi

All 2 ZIP codes in San Ramon → · California planting zones →

Questions about 94583

What planting zone is ZIP code 94583?

ZIP code 94583 (San Ramon, 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).

When is the last frost in San Ramon, CA?

The median last spring frost (32 °F) near 94583 is March 8; after April 15 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Mt Diablo Junction station.

When is the first frost in San Ramon, CA?

The median first fall frost near 94583 is December 22, giving a median frost-free growing season of 282 days.

When should I plant tomatoes in 94583?

Start tomato seeds indoors around Jan 11 – Jan 25 and set transplants outside around Mar 15 – Mar 29, one to three weeks after the median last frost.

How much rain and snow does 94583 get?

About 21.8 inches of precipitation a year (NOAA 1991–2020 normals, Castro Valley 0.4 Nne station).

How hot do summers get in San Ramon, CA?

The average high peaks at 83 °F in July, with about 27 days a year at 90 °F or more.

What kind of soil does 94583 have?

The USDA soil survey maps Botella at the center of ZIP 94583: clay loam, moderately well drained, pH about 6.0 (slightly acidic).

Did spring come early in San Ramon, CA in 2026?

Spring leaf-out near 94583 came on Jan 27 in 2026, 4 days earlier than the 1991–2020 average (Jan 31), according to the USA National Phenology Network Spring Index.

What kind of onions grow in San Ramon, CA?

Intermediate onions: the longest day near 94583 is 14 h 47 min, so day-neutral types bulb best; long-day varieties may not bulb fully.