Data: 2023 USDA zones (PRISM/OSU) · NOAA 1991–2020 normals · updated Oct 29, 2026

Planting zone for 91759 — Mount Baldy, CA

ZIP code 91759 (Mount Baldy, Los Angeles County) is in USDA zone 8a: the coldest winter night averages 10 to 15 °F. The median last spring frost is May 16 and the first fall frost October 13.

Where ZIP 91759 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.

Zone8a10 to 15 °F

Coldest night−12.2 to −9.4 °C

Last frostMay 16

First frostOct 13

2012 zone9a

Was 9a on the 2012 map — a full zone colder now. The zone is the one at the center of the ZIP code; hilly ZIPs can span two zones. What zone 8a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Mount Baldy, 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 Mount Baldy, CA

JanFebMarAprMayJunJulAugSepOctNovDec

Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free

Last spring frostMay 16median — 50% chance of a later frost

Safe for tender plantsJune 9only 10% chance of frost after

First fall frostOctober 13median — 10% chance by Sep 25

Growing season151 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 25 and returns around October 30.

From the NOAA station Wrightwood, CA — 7 miles away, elevation 6,001 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 91759

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Apr 4 – Apr 18

SpinachSow outdoors · Apr 4 – Apr 25

Broccoli, cabbageStart indoors · Mar 7 – Mar 21

Broccoli, cabbageTransplant · Apr 25 – May 9

Onion setsPlant outdoors · Apr 18 – May 2

PotatoesPlant outdoors · Apr 25 – May 9

LettuceSow outdoors · Apr 18 – May 2

Carrots, beetsSow outdoors · Apr 25 – May 9

TomatoesStart indoors · Mar 21 – Apr 4

TomatoesTransplant · May 23 – Jun 6

Peppers, eggplantStart indoors · Mar 7 – Mar 21

Peppers, eggplantTransplant · May 30 – Jun 13

BeansSow outdoors · May 23 – Jun 6

Sweet cornSow outdoors · May 23 – Jun 6

Cucumbers, squashSow outdoors · May 23 – Jun 6

Fall lettuce, spinachSow outdoors · Aug 18 – Sep 1

GarlicPlant cloves · Sep 29 – Nov 3

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 16) and first fall frost (Oct 13) 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 91759 came on Feb 13 — 8 days later than the 1991–2020 average (Feb 5).

average
Feb 52026
Feb 13

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 Mount Baldy, CA

The soil mapped at the center of ZIP 91759 is Stukel family — gravelly loam, somewhat excessively drained.

TextureGravelly loama good balance for most vegetables

pH6.6neutral; most vegetables like 6.0–7.0

DrainageSomewhat excessively drainednatural drainage class

Organic matter1%low — add compost

Hydrologic groupDwater soaks in very slowly

Farmland classNot prime farmlandUSDA classification

Map unit: Stukel-Sur-Winthrop families complex, 60 to 100 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 91759; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Mount Baldy, CA

Summer high83 °Faverage high, July

Winter low25 °Faverage low, February

Hot days4days a year at 90 °F or more

Freezing nights159nights a year at 32 °F or less

Growing degree days2,050base 50 °F — the season’s usable heat

Longest day14 h 27 mindaylight on June 21

Shortest day9 h 52 mindaylight on December 21

Onions to growIntermediateday-neutral types bulb best; long-day varieties may not bulb fully

Precipitation21.1 inper year, rain and melted snow

Snowfall62 inper year

Average high and low, by month

Precipitation by month inches · ❄ = snowfall

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Wrightwood, CA (7 mi away); precipitation: Wrightwood, CA (7 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

917029b

Azusa, CA · 6 mi

923977b

Wrightwood, CA · 7 mi

923588a

Lytle Creek, CA · 8 mi

Rancho Cucamonga, CA · 10 mi

California planting zones →

Questions about 91759

What planting zone is ZIP code 91759?

ZIP code 91759 (Mount Baldy, CA) is in USDA hardiness zone 8a on the 2023 map: the coldest night of an average winter reaches 10 to 15 °F (−12.2 to −9.4 °C).

When is the last frost in Mount Baldy, CA?

The median last spring frost (32 °F) near 91759 is May 16; after June 9 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Wrightwood station.

When is the first frost in Mount Baldy, CA?

The median first fall frost near 91759 is October 13, giving a median frost-free growing season of 151 days.

When should I plant tomatoes in 91759?

Start tomato seeds indoors around Mar 21 – Apr 4 and set transplants outside around May 23 – Jun 6, one to three weeks after the median last frost.

How much rain and snow does 91759 get?

About 21.1 inches of precipitation a year and 62 inches of snowfall (NOAA 1991–2020 normals, Wrightwood station).

How hot do summers get in Mount Baldy, CA?

The average high peaks at 83 °F in July, with about 4 days a year at 90 °F or more.

What kind of soil does 91759 have?

The USDA soil survey maps Stukel family at the center of ZIP 91759: gravelly loam, somewhat excessively drained, pH about 6.6 (neutral).

Did spring come early in Mount Baldy, CA in 2026?

Spring leaf-out near 91759 came on Feb 13 in 2026, 8 days later than the 1991–2020 average (Feb 5), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Mount Baldy, CA?

Intermediate onions: the longest day near 91759 is 14 h 27 min, so day-neutral types bulb best; long-day varieties may not bulb fully.

Did the zone for 91759 change?

Yes. The 2012 USDA map put 91759 in zone 9a; the 2023 map puts it in zone 8a. The newer map uses 1991–2020 data and more weather stations.