Garden Climate for Rancho San Diego & Spring Valley: 91978, 92019
Zone 10b · Last frost ~Jan 6 · Soil 69.6°F today (modeled) · See your place on the 2023 USDA zone map
ZIPs in this area
What differs between these ZIPs: elevation, soil temperature. Everything else on this page is the same for all of them. The page below shows 91978 (closest to the area's middle elevation).
| ZIP | Town | Elevation | Zone | Last frost | First frost | Chill hrs last season | Soil now |
|---|---|---|---|---|---|---|---|
| 91978 | Spring Valley | 513 ft | 10b | Jan 6 | Dec 21 | 56 | 69.6°F |
| 92019 | Rancho San Diego | 671 ft | 10b | Jan 6 | Dec 21 | 56 | 76.0°F |
Why grouped: these are urban and suburban lowland ZIPs (under about 1,500 ft and within 40 km of the ocean) whose numbers are close: median last frost dates within about two weeks of each other, last season's chill hours all in the <100 range, the same inland setting and the same 820 ft elevation band. Each ZIP still uses its own nearest suitable stations; see the table for exact values.
Public NOAA/USDA data, updated 2026-10-17 02:17 UTC.
USDA Plant Hardiness Zone Map · Spring Valley focus
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.
Frost dates for 91978
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.
7-day forecast · High / Low / Rain / Frost / Wind
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%.
Fruit that fits here
Want to know what fruit and berry varieties will grow well in your area? We rate 250+ peaches, citrus, avocados, figs, berries and more against your chill hours, frost and summer heat.
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.
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
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: CIMIS, California Department of Water Resources (hourly air temperature; QC-flagged hours dropped)
- Raw data: /data/zip/91978.json