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

Planting zone for 91916 — Descanso, CA

ZIP code 91916 (Descanso, San Diego County) is in USDA zone 9b: the coldest winter night averages 25 to 30 °F. The median last spring frost is April 19 and the first fall frost October 27.

Where ZIP 91916 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 frostApr 19
First frostOct 27
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 Descanso, 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 Descanso, CA

JanFebMarAprMayJunJulAugSepOctNovDec
Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free
Last spring frostApril 19median — 50% chance of a later frost
Safe for tender plantsMay 14only 10% chance of frost after
First fall frostOctober 27median — 10% chance by Oct 9
Growing season190 daysfrost-free, median

A hard freeze (28 °F) usually ends around March 14 and returns around November 12.

From the NOAA station Cuyamaca, CA — 6 miles away, elevation 4,639 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 91916

JanFebMarAprMayJunJulAugSepOctNovDec
PeasSow outdoors · Mar 8 – Mar 22
SpinachSow outdoors · Mar 8 – Mar 29
Broccoli, cabbageStart indoors · Feb 8 – Feb 22
Broccoli, cabbageTransplant · Mar 29 – Apr 12
Onion setsPlant outdoors · Mar 22 – Apr 5
PotatoesPlant outdoors · Mar 29 – Apr 12
LettuceSow outdoors · Mar 22 – Apr 5
Carrots, beetsSow outdoors · Mar 29 – Apr 12
TomatoesStart indoors · Feb 22 – Mar 8
TomatoesTransplant · Apr 26 – May 10
Peppers, eggplantStart indoors · Feb 8 – Feb 22
Peppers, eggplantTransplant · May 3 – May 17
BeansSow outdoors · Apr 26 – May 10
Sweet cornSow outdoors · Apr 26 – May 10
Cucumbers, squashSow outdoors · Apr 26 – May 10
Fall lettuce, spinachSow outdoors · Sep 1 – Sep 15
GarlicPlant cloves · Oct 13 – Nov 17
Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (Apr 19) and first fall frost (Oct 27) 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 91916 came on Jan 19 — 14 days earlier than the 1991–2020 average (Feb 2).

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 Descanso, CA

The soil mapped at the center of ZIP 91916 is Cieneba — coarse sandy loam, somewhat excessively drained.

TextureCoarse sandy loamdrains and warms fast; dries out and needs more feeding
pH5.8moderately acidic; most vegetables like 6.0–7.0
DrainageSomewhat excessively drainednatural drainage class
Organic matter0.75%low — add compost
Hydrologic groupDwater soaks in very slowly
Farmland classNot prime farmlandUSDA classification

Map unit: Cieneba rocky coarse sandy loam, 9 to 30 percent slopes, eroded.

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 91916; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Descanso, CA

Summer high84 °Faverage high, August
Winter low32 °Faverage low, December
Hot days19days a year at 90 °F or more
Freezing nights87nights a year at 32 °F or less
Growing degree days2,729base 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
Precipitation21.4 inper year, rain and melted snow

Average high and low, by month

20°30°40°50°60°70°80°90°32 °FJanuary: average high 51 °F, low 33 °F 51°33° JanFebruary: average high 51 °F, low 34 °F 51°34° FebMarch: average high 55 °F, low 36 °F 55°36° MarApril: average high 60 °F, low 39 °F 60°39° AprMay: average high 67 °F, low 44 °F 67°44° MayJune: average high 76 °F, low 51 °F 76°51° JunJuly: average high 83 °F, low 58 °F 83°58° JulAugust: average high 84 °F, low 58 °F 84°58° AugSeptember: average high 79 °F, low 51 °F 79°51° SepOctober: average high 69 °F, low 42 °F 69°42° OctNovember: average high 59 °F, low 35 °F 59°35° NovDecember: average high 51 °F, low 32 °F 51°32° Dec

Precipitation by month inches

0″1″2″3″4″5″January: 3.79 in precipitation 3.8 JanFebruary: 4.53 in precipitation 4.5 FebMarch: 3.38 in precipitation 3.4 MarApril: 1.35 in precipitation 1.4 AprMay: 0.96 in precipitation 1.0 MayJune: 0.09 in precipitation 0.1 JunJuly: 0.30 in precipitation 0.3 JulAugust: 0.21 in precipitation 0.2 AugSeptember: 0.37 in precipitation 0.4 SepOctober: 0.99 in precipitation 1.0 OctNovember: 1.89 in precipitation 1.9 NovDecember: 3.49 in precipitation 3.5 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Cuyamaca, CA (6 mi away); precipitation: Descanso 3.7n, CA (within 1 mile). Daylight is calculated from latitude.

Nearby ZIP codes

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

919318b
Guatay, CA · 6 mi
919628b
Pine Valley, CA · 8 mi
919019b
Alpine, CA · 9 mi
919039b
Alpine, CA · 9 mi
919488a
Mount Laguna, CA · 10 mi
920659b
Ramona, CA · 15 mi
9202110a
El Cajon, CA · 15 mi
9204010a
Lakeside, CA · 15 mi

California planting zones →

Questions about 91916

What planting zone is ZIP code 91916?

ZIP code 91916 (Descanso, 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 Descanso, CA?

The median last spring frost (32 °F) near 91916 is April 19; after May 14 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Cuyamaca station.

When is the first frost in Descanso, CA?

The median first fall frost near 91916 is October 27, giving a median frost-free growing season of 190 days.

When should I plant tomatoes in 91916?

Start tomato seeds indoors around Feb 22 – Mar 8 and set transplants outside around Apr 26 – May 10, one to three weeks after the median last frost.

How much rain and snow does 91916 get?

About 21.4 inches of precipitation a year (NOAA 1991–2020 normals, Descanso 3.7n station).

How hot do summers get in Descanso, CA?

The average high peaks at 84 °F in August, with about 19 days a year at 90 °F or more.

What kind of soil does 91916 have?

The USDA soil survey maps Cieneba at the center of ZIP 91916: coarse sandy loam, somewhat excessively drained, pH about 5.8 (moderately acidic).

Did spring come early in Descanso, CA in 2026?

Spring leaf-out near 91916 came on Jan 19 in 2026, 14 days earlier than the 1991–2020 average (Feb 2), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Descanso, CA?

Intermediate onions: the longest day near 91916 is 14 h 19 min, so day-neutral types bulb best; long-day varieties may not bulb fully.

Did the zone for 91916 change?

Yes. The 2012 USDA map put 91916 in zone 9a; the 2023 map puts it in zone 9b. The newer map uses 1991–2020 data and more weather stations.