Garden Climate for El Cajon, CA 92021

Zone 10a · Last frost ~Jan 6 · Soil 69.0°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 · El Cajon focus

2023 USDA Plant Hardiness Zone Map around ZIP 92021, marker at El Cajon, CA
7a7b8a8b9a9b10a10b11a

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
10a
USDA 2023 · 30 to 35°F
Last frost
Jan 6
avg last frost (50%)
Soil temp Modeled
69.0°F
↓ 8.2° in 7 days
Chill hours
—
starts Nov 1
Rain
1.31″
since Oct 1 · normal 0.19″

Frost dates for 92021

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) 2.0 km away 27 yrs of record · 240 ft lower than this ZIP

Newsletter · 92021

Frost alerts and planting reminders for 92021. 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
87° 71° gust 55 mph 💧12%
High wind
Sat 17
85° 63° gust 44 mph 💧12%
High wind
Sun 18
84° 63° gust 18 mph 💧0%
Clear
Mon 19
81° 59° gust 15 mph 💧8%
Clear
Tue 20
71° 56° gust 30 mph 💧66% · 0.03″
Rain
Wed 21
67° 54° gust 23 mph 💧66% · 0.51″
Rain
Thu 22
67° 53° gust 18 mph 💧30% · 0.07″
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 · 92021

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 92021

What USDA hardiness zone is 92021?

ZIP 92021 (El Cajon, CA) is in USDA zone 10a (30 to 35°F average annual extreme minimum), per the 2023 USDA Plant Hardiness Zone Map.

When is the last frost in 92021?

Based on NOAA 1991–2020 normals at Ca El Cajon (2.0 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

92019 El Cajon 92040 Lakeside 92020 El Cajon 92071 Santee 91901 Alpine 91941 La Mesa

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) 2.0 km away 27 yrs of record · 240 ft lower than this ZIP
  • 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/92021.json