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

Planting zone for 91948 — Mount Laguna, CA

ZIP code 91948 (Mount Laguna, San Diego County) is in USDA zone 8a: the coldest winter night averages 10 to 15 °F. The median last spring frost is April 22 and the first fall frost November 8.

Where ZIP 91948 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 frostApr 22
First frostNov 8
2012 zone8a

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 8a means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Mount Laguna, 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 Laguna, CA

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostApril 22median — 50% chance of a later frost
Safe for tender plantsMay 21only 10% chance of frost after
First fall frostNovember 8median — 10% chance by Oct 10
Growing season197 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 2 and returns around December 1.

From the NOAA station Mt Laguna #3, CA — 3 miles away, elevation 5,919 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 91948

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 11 – Mar 25
SpinachSow outdoors · Mar 11 – Apr 1
Broccoli, cabbageStart indoors · Feb 11 – Feb 25
Broccoli, cabbageTransplant · Apr 1 – Apr 15
Onion setsPlant outdoors · Mar 25 – Apr 8
PotatoesPlant outdoors · Apr 1 – Apr 15
LettuceSow outdoors · Mar 25 – Apr 8
Carrots, beetsSow outdoors · Apr 1 – Apr 15
TomatoesStart indoors · Feb 25 – Mar 11
TomatoesTransplant · Apr 29 – May 13
Peppers, eggplantStart indoors · Feb 11 – Feb 25
Peppers, eggplantTransplant · May 6 – May 20
BeansSow outdoors · Apr 29 – May 13
Sweet cornSow outdoors · Apr 29 – May 13
Cucumbers, squashSow outdoors · Apr 29 – May 13
Fall lettuce, spinachSow outdoors · Sep 13 – Sep 27
GarlicPlant cloves · Oct 25 – Nov 29
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 22) and first fall frost (Nov 8) 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 91948 came on Feb 3 — 18 days earlier than the 1991–2020 average (Feb 21).

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 Laguna, CA

The soil mapped at the center of ZIP 91948 is Crouch — stony coarse sandy loam, well drained.

TextureStony coarse sandy loamdrains and warms fast; dries out and needs more feeding
pH6.5neutral; most vegetables like 6.0–7.0
DrainageWell drainednatural drainage class
Organic matter1.5%low — add compost
Hydrologic groupAwater soaks in fast
Farmland classNot prime farmlandUSDA classification

Map unit: Crouch stony coarse sandy loam, 5 to 30 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 91948; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Mount Laguna, CA

Summer high83 °Faverage high, July
Winter low33 °Faverage low, January
Hot days4days a year at 90 °F or more
Freezing nights63nights a year at 32 °F or less
Growing degree days2,908base 50 °F — the season’s usable heat
Longest day14 h 19 mindaylight on June 21
Shortest day9 h 59 mindaylight on December 21
Onions to growIntermediateday-neutral types bulb best; long-day varieties may not bulb fully
Precipitation17.6 inper year, rain and melted snow

Average high and low, by month

20°30°40°50°60°70°80°90°32 °FJanuary: average high 50 °F, low 33 °F 50°33° JanFebruary: average high 50 °F, low 34 °F 50°34° FebMarch: average high 54 °F, low 36 °F 54°36° MarApril: average high 61 °F, low 40 °F 61°40° AprMay: average high 68 °F, low 46 °F 68°46° MayJune: average high 78 °F, low 53 °F 78°53° JunJuly: average high 83 °F, low 60 °F 83°60° JulAugust: average high 82 °F, low 58 °F 82°58° AugSeptember: average high 76 °F, low 54 °F 76°54° SepOctober: average high 67 °F, low 45 °F 67°45° OctNovember: average high 57 °F, low 38 °F 57°38° NovDecember: average high 51 °F, low 34 °F 51°34° Dec

Precipitation by month inches

0″1″2″3″4″5″January: 2.69 in precipitation 2.7 JanFebruary: 4.82 in precipitation 4.8 FebMarch: 2.59 in precipitation 2.6 MarApril: 0.90 in precipitation 0.9 AprMay: 0.40 in precipitation 0.4 MayJune: 0.08 in precipitation 0.1 JunJuly: 0.75 in precipitation 0.8 JulAugust: 0.49 in precipitation 0.5 AugSeptember: 0.53 in precipitation 0.5 SepOctober: 0.70 in precipitation 0.7 OctNovember: 1.39 in precipitation 1.4 NovDecember: 2.30 in precipitation 2.3 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Mt Laguna #3, CA (3 mi away); precipitation: Mt Laguna #3, CA (3 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

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

919628b
Pine Valley, CA · 3 mi
919318b
Guatay, CA · 7 mi
919169b
Descanso, CA · 10 mi
919069a
Campo, CA · 14 mi
919019b
Alpine, CA · 15 mi
919059a
Boulevard, CA · 16 mi
919639a
Potrero, CA · 17 mi
920369b
Julian, CA · 17 mi

California planting zones →

Questions about 91948

What planting zone is ZIP code 91948?

ZIP code 91948 (Mount Laguna, 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 Laguna, CA?

The median last spring frost (32 °F) near 91948 is April 22; after May 21 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Mt Laguna #3 station.

When is the first frost in Mount Laguna, CA?

The median first fall frost near 91948 is November 8, giving a median frost-free growing season of 197 days.

When should I plant tomatoes in 91948?

Start tomato seeds indoors around Feb 25 – Mar 11 and set transplants outside around Apr 29 – May 13, one to three weeks after the median last frost.

How much rain and snow does 91948 get?

About 17.6 inches of precipitation a year (NOAA 1991–2020 normals, Mt Laguna #3 station).

How hot do summers get in Mount Laguna, 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 91948 have?

The USDA soil survey maps Crouch at the center of ZIP 91948: stony coarse sandy loam, well drained, pH about 6.5 (neutral).

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

Spring leaf-out near 91948 came on Feb 3 in 2026, 18 days earlier than the 1991–2020 average (Feb 21), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Mount Laguna, CA?

Intermediate onions: the longest day near 91948 is 14 h 19 min, so day-neutral types bulb best; long-day varieties may not bulb fully.