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

Planting zone for 95987 — Williams, CA

ZIP code 95987 (Williams, Colusa County) is in USDA zone 9b: the coldest winter night averages 25 to 30 °F. The median last spring frost is February 14 and the first fall frost December 1.

Where ZIP 95987 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 frostFeb 14
First frostDec 1
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 Williams, 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 Williams, CA

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostFebruary 14median — 50% chance of a later frost
Safe for tender plantsMarch 31only 10% chance of frost after
First fall frostDecember 1median — 10% chance by Nov 11
Growing season293 daysfrost-free, median

A hard freeze (28 °F) usually ends around January 8 and returns around December 15.

From the NOAA station Colusa 2 Ssw, CA — 13 miles away, elevation 49 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 95987

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Jan 3 – Jan 17
SpinachSow outdoors · Jan 3 – Jan 24
Broccoli, cabbageStart indoors · Dec 6 – Dec 20
Broccoli, cabbageTransplant · Jan 24 – Feb 7
Onion setsPlant outdoors · Jan 17 – Jan 31
PotatoesPlant outdoors · Jan 24 – Feb 7
LettuceSow outdoors · Jan 17 – Jan 31
Carrots, beetsSow outdoors · Jan 24 – Feb 7
TomatoesStart indoors · Dec 20 – Jan 3
TomatoesTransplant · Feb 21 – Mar 7
Peppers, eggplantStart indoors · Dec 6 – Dec 20
Peppers, eggplantTransplant · Feb 28 – Mar 14
BeansSow outdoors · Feb 21 – Mar 7
Sweet cornSow outdoors · Feb 21 – Mar 7
Cucumbers, squashSow outdoors · Feb 21 – Mar 7
Fall lettuce, spinachSow outdoors · Oct 6 – Oct 20
GarlicPlant cloves · Nov 17 – Dec 22
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Feb 14) and first fall frost (Dec 1) 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 95987 came on Jan 29 — 3 days earlier than the 1991–2020 average (Feb 1).

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 Williams, CA

The soil mapped at the center of ZIP 95987 is Ayar — clay, well drained.

TextureClayholds water and nutrients; slow to drain and warm up
pH7.9alkaline; most vegetables like 6.0–7.0
DrainageWell drainednatural drainage class
Organic matter2%moderate
Hydrologic groupCwater soaks in slowly
Farmland classNot prime farmlandUSDA classification

Map unit: Ayar clay, 5 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 95987; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Williams, CA

Summer high92 °Faverage high, July
Winter low38 °Faverage low, January
Hot days85days a year at 90 °F or more
Freezing nights17nights a year at 32 °F or less
Growing degree days4,582base 50 °F — the season’s usable heat
Longest day14 h 55 mindaylight on June 21
Shortest day9 h 25 mindaylight on December 21
Onions to growIntermediateday-neutral types bulb best; long-day varieties may not bulb fully
Precipitation17.2 inper year, rain and melted snow

Average high and low, by month

30°40°50°60°70°80°90°100°32 °FJanuary: average high 55 °F, low 38 °F 55°38° JanFebruary: average high 60 °F, low 41 °F 60°41° FebMarch: average high 67 °F, low 44 °F 67°44° MarApril: average high 73 °F, low 46 °F 73°46° AprMay: average high 81 °F, low 53 °F 81°53° MayJune: average high 88 °F, low 59 °F 88°59° JunJuly: average high 92 °F, low 60 °F 92°60° JulAugust: average high 92 °F, low 58 °F 92°58° AugSeptember: average high 89 °F, low 54 °F 89°54° SepOctober: average high 79 °F, low 48 °F 79°48° OctNovember: average high 64 °F, low 42 °F 64°42° NovDecember: average high 55 °F, low 38 °F 55°38° Dec

Precipitation by month inches

0″1″2″3″4″January: 3.58 in precipitation 3.6 JanFebruary: 2.97 in precipitation 3.0 FebMarch: 2.19 in precipitation 2.2 MarApril: 1.00 in precipitation 1.0 AprMay: 0.84 in precipitation 0.8 MayJune: 0.51 in precipitation 0.5 JunJuly: 0.01 in precipitation 0.0 JulAugust: 0.03 in precipitation 0.0 AugSeptember: 0.11 in precipitation 0.1 SepOctober: 0.87 in precipitation 0.9 OctNovember: 1.91 in precipitation 1.9 NovDecember: 3.17 in precipitation 3.2 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Colusa 2 Ssw, CA (13 mi away); precipitation: Colusa 2 Ssw, CA (13 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

959129b
Arbuckle, CA · 12 mi
956799b
Rumsey, CA · 13 mi
959559b
Maxwell, CA · 13 mi
959329b
Colusa, CA · 16 mi
956379b
Guinda, CA · 17 mi
959799a
Stonyford, CA · 18 mi
959509b
Grimes, CA · 18 mi
956079a
Capay, CA · 20 mi

California planting zones →

Questions about 95987

What planting zone is ZIP code 95987?

ZIP code 95987 (Williams, 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 Williams, CA?

The median last spring frost (32 °F) near 95987 is February 14; after March 31 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Colusa 2 Ssw station.

When is the first frost in Williams, CA?

The median first fall frost near 95987 is December 1, giving a median frost-free growing season of 293 days.

When should I plant tomatoes in 95987?

Start tomato seeds indoors around Dec 20 – Jan 3 and set transplants outside around Feb 21 – Mar 7, one to three weeks after the median last frost.

How much rain and snow does 95987 get?

About 17.2 inches of precipitation a year (NOAA 1991–2020 normals, Colusa 2 Ssw station).

How hot do summers get in Williams, CA?

The average high peaks at 92 °F in July, with about 85 days a year at 90 °F or more.

What kind of soil does 95987 have?

The USDA soil survey maps Ayar at the center of ZIP 95987: clay, well drained, pH about 7.9 (alkaline).

Did spring come early in Williams, CA in 2026?

Spring leaf-out near 95987 came on Jan 29 in 2026, 3 days earlier than the 1991–2020 average (Feb 1), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Williams, CA?

Intermediate onions: the longest day near 95987 is 14 h 55 min, so day-neutral types bulb best; long-day varieties may not bulb fully.