Garden Climate for Spring Valley, CA 91978

Zone 10b · Last frost ~Jan 6 · Soil 65.5°F today (modeled) · See your place on the 2023 USDA zone map

This ZIP is part of El Cajon, La Mesa, Lakeside area, where nearby ZIPs share the same stations and zone. That page compares every ZIP in the area.

Public NOAA/USDA data, updated 2026-10-16 19:24 UTC.

USDA Plant Hardiness Zone Map · Spring Valley focus

2023 USDA Plant Hardiness Zone Map around ZIP 91978, marker at Spring Valley, CA
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USDA Plant Hardiness Zone Map, 2023. Agricultural Research Service, U.S. Department of Agriculture. Accessed from https://planthardiness.ars.usda.gov/. Rendered unaltered from the PRISM Group, Oregon State University GIS data (https://prism.oregonstate.edu, accessed 15 Oct 2026) with official zone colors. Roads (TIGER/Line 2023 primary roads), place names (2023 Gazetteer) and state lines (2023 cartographic boundaries 1:500k) are drawn on top. Source: U.S. Census Bureau.

Zone
10b
USDA 2023 · 35 to 40°F
Last frost
Jan 6
avg last frost (50%)
Soil temp Modeled
65.5°F
↓ 8.6° in 7 days
Chill hours
—
starts Nov 1
Rain
1.31″
since Oct 1 · normal 0.19″

Frost dates for 91978

Last spring frost
Jan 6
50% odds
First fall frost
Dec 21
50% odds
Safer spring date
Feb 7
10% chance of later frost
Growing season
350
days (50%)

Earliest-risk fall date (10%): Dec 1.

NOAA NCEI U.S. Climate Normals 1991-2020, annual/seasonal freeze probabilities (32F) · CA EL CAJON (USC00042706) 8.1 km away 27 yrs of record · about the same elevation

Newsletter · 91978

Frost alerts and planting reminders for 91978. Coming soon.

Ad strip · leaderboard 970×90 / 728×90

7-day forecast · High / Low / Rain / Frost / Wind

High wind: 2 day(s) with gusts ≥40 mph. Stake and protect transplants.
Fri 16
86° 70° gust 54 mph 💧8%
High wind
Sat 17
83° 61° gust 41 mph 💧8%
High wind
Sun 18
82° 61° gust 17 mph 💧0%
Clear
Mon 19
78° 58° gust 17 mph 💧7%
Clear
Tue 20
68° 55° gust 26 mph 💧67% · 0.06″
Rain
Wed 21
65° 54° gust 25 mph 💧67% · 0.46″
Rain
Thu 22
64° 53° gust 20 mph 💧31% · 0.10″
Clear

NOAA NWS api.weather.gov (SGX). Frost = low ≤32°F · High wind = gust ≥40 mph · 💧 = chance of precipitation and expected amount (NWS quantitative precipitation forecast; blank when NWS gives none) · Rain = chance ≥50%.

What to grow when · 91978

Calendar: San Diego County, inland valleys (guide Regions 3-4). Planting months from UC Master Gardeners of San Diego County; Master Gardener Association of San Diego County. Harvest months add typical days-to-harvest. This month also checks live soil temperature and the 7-day frost forecast. The harvest planner uses the same calendar. Rules: methodology.

Affiliate links (disclosed). Placeholders, no partners yet:Frost clothSoil thermometer

Questions about 91978

What USDA hardiness zone is 91978?

ZIP 91978 (Spring Valley, CA) is in USDA zone 10b (35 to 40°F average annual extreme minimum), per the 2023 USDA Plant Hardiness Zone Map.

When is the last frost in 91978?

Based on NOAA 1991–2020 normals at Ca El Cajon (8.1 km away), the median last 32°F freeze is Jan 6. In 1 of 10 years it is after Feb 7. The median first fall freeze is Dec 21.

Nearby ZIP codes

91914 Chula Vista 91977 Spring Valley 91902 Bonita 91915 Chula Vista 91941 La Mesa 91913 Chula Vista

Sources for this page

  • Location: US Census Bureau 2023 Gazetteer, ZCTA internal point
  • Zone: USDA Plant Hardiness Zone Map 2023, ZIP datasets (USDA ARS + PRISM Climate Group, Oregon State University)
  • Frost: NOAA NCEI U.S. Climate Normals 1991-2020, annual/seasonal freeze probabilities (32F) CA EL CAJON (USC00042706) 8.1 km away 27 yrs of record · about the same elevation
  • Forecast: NOAA National Weather Service api.weather.gov (7-day forecast + gridpoint wind gusts)
  • Soil: Open-Meteo forecast API soil model (non-commercial terms)
  • Chill: Iowa Environmental Mesonet ASOS archive (NWS/FAA METAR routine + special obs; one value per clock hour)
  • Raw data: /data/zip/91978.json