Garden Climate for La Mesa, CA 91942

Zone 10b · Last frost ~Jan 6 · Soil 70.8°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 · La Mesa focus

2023 USDA Plant Hardiness Zone Map around ZIP 91942, marker at La Mesa, 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
70.8°F
↓ 6.8° in 7 days
Chill hours
—
starts Nov 1
Rain
1.31″
since Oct 1 · normal 0.19″

Frost dates for 91942

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) 8.7 km away 27 yrs of record · 85 ft lower than this ZIP

Newsletter · 91942

Frost alerts and planting reminders for 91942. Coming soon.

Ad strip · leaderboard 970×90 / 728×90

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

Fri 16
92° 71° gust 35 mph 💧6%
Clear
Sat 17
89° 64° gust 22 mph 💧6%
Clear
Sun 18
88° 64° gust 16 mph 💧0%
Clear
Mon 19
83° 62° gust 15 mph 💧8%
Clear
Tue 20
73° 59° gust 25 mph 💧68% · 0.05″
Rain
Wed 21
70° 57° gust 23 mph 💧68% · 0.45″
Rain
Thu 22
68° 57° gust 17 mph 💧31% · 0.11″
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 · 91942

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 91942

What USDA hardiness zone is 91942?

ZIP 91942 (La Mesa, 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 91942?

Based on NOAA 1991–2020 normals at Ca El Cajon (8.7 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

91941 La Mesa 92119 San Diego 92182 San Diego 92115 San Diego 91945 Lemon Grove 92020 El Cajon

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) 8.7 km away 27 yrs of record · 85 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/91942.json