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

Planting zone for 95951 — Hamilton City, CA

ZIP code 95951 (Hamilton City, Glenn County) is in USDA zone 9b: the coldest winter night averages 25 to 30 °F. The median last spring frost is March 4 and the first fall frost November 17.

Where ZIP 95951 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 4
First frostNov 17
2012 zone9a

Was 9a on the 2012 map — half a zone warmer now. 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 Hamilton City, 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 Hamilton City, CA

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostMarch 4median — 50% chance of a later frost
Safe for tender plantsApril 2only 10% chance of frost after
First fall frostNovember 17median — 10% chance by Nov 1
Growing season257 daysfrost-free, median

A hard freeze (28 °F) usually ends around February 5 and returns around December 3.

From the NOAA station Chico Univ Farm, CA — 10 miles away, elevation 184 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 95951

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Jan 21 – Feb 4
SpinachSow outdoors · Jan 21 – Feb 11
Broccoli, cabbageStart indoors · Dec 24 – Jan 7
Broccoli, cabbageTransplant · Feb 11 – Feb 25
Onion setsPlant outdoors · Feb 4 – Feb 18
PotatoesPlant outdoors · Feb 11 – Feb 25
LettuceSow outdoors · Feb 4 – Feb 18
Carrots, beetsSow outdoors · Feb 11 – Feb 25
TomatoesStart indoors · Jan 7 – Jan 21
TomatoesTransplant · Mar 11 – Mar 25
Peppers, eggplantStart indoors · Dec 24 – Jan 7
Peppers, eggplantTransplant · Mar 18 – Apr 1
BeansSow outdoors · Mar 11 – Mar 25
Sweet cornSow outdoors · Mar 11 – Mar 25
Cucumbers, squashSow outdoors · Mar 11 – Mar 25
Fall lettuce, spinachSow outdoors · Sep 22 – Oct 6
GarlicPlant cloves · Nov 3 – Dec 8
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Mar 4) and first fall frost (Nov 17) 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 95951 came on Jan 31 — about the same time as 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 Hamilton City, CA

The soil mapped at the center of ZIP 95951 is Wyo — silt loam, well drained.

TextureSilt loama good balance for most vegetables
pH6.7neutral; most vegetables like 6.0–7.0
DrainageWell drainednatural drainage class
Organic matter1.25%low — add compost
Hydrologic groupBwater soaks in moderately
Farmland classPrime farmland if irrigatedUSDA classification

Map unit: Wyo silt loam.

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 95951; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Hamilton City, CA

Summer high95 °Faverage high, July
Winter low36 °Faverage low, January
Hot days99days a year at 90 °F or more
Freezing nights40nights a year at 32 °F or less
Growing degree days4,667base 50 °F — the season’s usable heat
Longest day14 h 59 mindaylight on June 21
Shortest day9 h 21 mindaylight on December 21
Onions to growIntermediateday-neutral types bulb best; long-day varieties may not bulb fully
Precipitation28.4 inper year, rain and melted snow

Average high and low, by month

30°40°50°60°70°80°90°100°110°32 °FJanuary: average high 56 °F, low 36 °F 56°36° JanFebruary: average high 62 °F, low 38 °F 62°38° FebMarch: average high 67 °F, low 42 °F 67°42° MarApril: average high 73 °F, low 45 °F 73°45° AprMay: average high 81 °F, low 52 °F 81°52° MayJune: average high 89 °F, low 57 °F 89°57° JunJuly: average high 95 °F, low 61 °F 95°61° JulAugust: average high 94 °F, low 59 °F 94°59° AugSeptember: average high 91 °F, low 55 °F 91°55° SepOctober: average high 80 °F, low 47 °F 80°47° OctNovember: average high 65 °F, low 40 °F 65°40° NovDecember: average high 57 °F, low 36 °F 57°36° Dec

Precipitation by month inches

0″1″2″3″4″5″6″January: 5.64 in precipitation 5.6 JanFebruary: 4.87 in precipitation 4.9 FebMarch: 3.94 in precipitation 3.9 MarApril: 2.20 in precipitation 2.2 AprMay: 1.39 in precipitation 1.4 MayJune: 0.65 in precipitation 0.7 JunJuly: 0.04 in precipitation 0.0 JulAugust: 0.14 in precipitation 0.1 AugSeptember: 0.27 in precipitation 0.3 SepOctober: 1.77 in precipitation 1.8 OctNovember: 2.61 in precipitation 2.6 NovDecember: 4.83 in precipitation 4.8 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Chico Univ Farm, CA (10 mi away); precipitation: Chico 2.9 W, CA (8 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

959279a
Chico, CA · 7 mi
959299a
Chico, CA · 8 mi
959269b
Chico, CA · 9 mi
959769a
Chico, CA · 9 mi
959289b
Chico, CA · 9 mi
959439b
Glenn, CA · 10 mi
959139b
Artois, CA · 12 mi
959739b
Chico, CA · 13 mi

California planting zones →

Questions about 95951

What planting zone is ZIP code 95951?

ZIP code 95951 (Hamilton City, 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 Hamilton City, CA?

The median last spring frost (32 °F) near 95951 is March 4; after April 2 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Chico Univ Farm station.

When is the first frost in Hamilton City, CA?

The median first fall frost near 95951 is November 17, giving a median frost-free growing season of 257 days.

When should I plant tomatoes in 95951?

Start tomato seeds indoors around Jan 7 – Jan 21 and set transplants outside around Mar 11 – Mar 25, one to three weeks after the median last frost.

How much rain and snow does 95951 get?

About 28.4 inches of precipitation a year (NOAA 1991–2020 normals, Chico 2.9 W station).

How hot do summers get in Hamilton City, CA?

The average high peaks at 95 °F in July, with about 99 days a year at 90 °F or more.

What kind of soil does 95951 have?

The USDA soil survey maps Wyo at the center of ZIP 95951: silt loam, well drained, pH about 6.7 (neutral).

Did spring come early in Hamilton City, CA in 2026?

Spring leaf-out near 95951 came on Jan 31 in 2026, about the same as the 1991–2020 average (Feb 1), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Hamilton City, CA?

Intermediate onions: the longest day near 95951 is 14 h 59 min, so day-neutral types bulb best; long-day varieties may not bulb fully.

Did the zone for 95951 change?

Yes. The 2012 USDA map put 95951 in zone 9a; the 2023 map puts it in zone 9b. The newer map uses 1991–2020 data and more weather stations.