Planting zone for 92278 — Twentynine Palms, CA
ZIP code 92278 (Twentynine Palms, San Bernardino County) is in USDA zone 9b: the coldest winter night averages 25 to 30 °F. The median last spring frost is January 24 and the first fall frost December 10.
Where ZIP 92278 is
Outlined: the ZIP code area · tap the map for the zone at any spot · scroll or pinch to zoomNot 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.
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 ServiceLoading the forecast for Twentynine Palms, 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 Twentynine Palms, CA
A hard freeze (28 °F) usually ends around January 3 and returns around December 23.
From the NOAA station Twentynine Palms, CA — 7 miles away, elevation 1,975 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 92278
Counted from the median last spring frost (Jan 24) and first fall frost (Dec 10) 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 92278 came on Jan 21 — 7 days earlier than the 1991–2020 average (Jan 28).
Jan 282026
Jan 21
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 Twentynine Palms, CA
The soil mapped at the center of ZIP 92278 is Cajon — coarse sand, somewhat excessively drained. Much of the area is built over (urban land); this is the natural soil underneath.
Map unit: Urban land-Cajon complex, 2 to 8 percent slpoes.
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 92278; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.
Climate in Twentynine Palms, CA
Average high and low, by month
Precipitation by month inches
NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Twentynine Palms, CA (7 mi away); precipitation: Twentynine Palms 0.3 Nne, CA (6 mi away). Daylight is calculated from latitude.
Nearby ZIP codes
8 of the 8 nearest ZIP codes are in a different zone — elevation and distance from water change winter lows quickly.
All 2 ZIP codes in Twentynine Palms → · California planting zones →
Questions about 92278
What planting zone is ZIP code 92278?
ZIP code 92278 (Twentynine Palms, 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 Twentynine Palms, CA?
The median last spring frost (32 °F) near 92278 is January 24; after February 22 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Twentynine Palms station.
When is the first frost in Twentynine Palms, CA?
The median first fall frost near 92278 is December 10, giving a median frost-free growing season of 321 days.
When should I plant tomatoes in 92278?
Start tomato seeds indoors around Nov 29 – Dec 13 and set transplants outside around Jan 31 – Feb 14, one to three weeks after the median last frost.
How much rain and snow does 92278 get?
About 4.8 inches of precipitation a year (NOAA 1991–2020 normals, Twentynine Palms 0.3 Nne station).
How hot do summers get in Twentynine Palms, CA?
The average high peaks at 104 °F in July, with about 154 days a year at 90 °F or more.
What kind of soil does 92278 have?
The USDA soil survey maps Cajon at the center of ZIP 92278: coarse sand, somewhat excessively drained, pH about 8.8 (alkaline).
Did spring come early in Twentynine Palms, CA in 2026?
Spring leaf-out near 92278 came on Jan 21 in 2026, 7 days earlier than the 1991–2020 average (Jan 28), according to the USA National Phenology Network Spring Index.
What kind of onions grow in Twentynine Palms, CA?
Intermediate onions: the longest day near 92278 is 14 h 27 min, so day-neutral types bulb best; long-day varieties may not bulb fully.
Did the zone for 92278 change?
Yes. The 2012 USDA map put 92278 in zone 9a; the 2023 map puts it in zone 9b. The newer map uses 1991–2020 data and more weather stations.