Data: 2023 USDA zones (PRISM/OSU) · NOAA 1991–2020 normals · updated

Planting zone for 92508 — Riverside, CA

ZIP code 92508 (Riverside, Riverside County) is in USDA zone 9b: the coldest winter night averages 25 to 30 °F.

Where ZIP 92508 is

Outlined: the ZIP code area · tap the map for the zone at any spot · scroll or pinch to zoom

Not 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.

Zone9b25 to 30 °F
Coldest night−3.9 to −1.1 °C
Last frostrare
First frostrare
2012 zone9b

Same zone as on the 2012 map. 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 Service

Loading the forecast for Riverside, 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

A 32 °F frost doesn't happen here in most winters. At the nearest station (NOAA station Riverside Fire Stn 3, CA — 6 miles away, elevation 840 ft) the median growing season is 353 days. When frost does come, it is a midwinter night or two; cover tender plants when a freeze is forecast.

Frost data: NOAA NCEI U.S. Climate Normals 1991–2020.

When spring arrived in 2026

In 2026, spring leaf-out near 92508 came on Jan 18 — 6 days earlier than the 1991–2020 average (Jan 24).

JanFebMarAprMayJun

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 Riverside, CA

The soil mapped at the center of ZIP 92508 is Fallbrook — sandy loam, well drained.

TextureSandy loamdrains and warms fast; dries out and needs more feeding
pH6.5neutral; most vegetables like 6.0–7.0
DrainageWell drainednatural drainage class
Organic matter0.75%low — add compost
Hydrologic groupCwater soaks in slowly
Farmland classNot prime farmlandUSDA classification

Map unit: Fallbrook sandy loam, 15 to 25 percent slopes, eroded.

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 92508; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Riverside, CA

Summer high95 °Faverage high, August
Winter low37 °Faverage low, January
Hot days100days a year at 90 °F or more
Freezing nights25nights a year at 32 °F or less
Growing degree days5,035base 50 °F — the season’s usable heat
Longest day14 h 25 mindaylight on June 21
Shortest day9 h 54 mindaylight on December 21
Onions to growIntermediateday-neutral types bulb best; long-day varieties may not bulb fully
Precipitation10.7 inper year, rain and melted snow

Average high and low, by month

30°40°50°60°70°80°90°100°110°32 °FJanuary: average high 66 °F, low 37 °F 66°37° JanFebruary: average high 66 °F, low 38 °F 66°38° FebMarch: average high 71 °F, low 40 °F 71°40° MarApril: average high 74 °F, low 44 °F 74°44° AprMay: average high 80 °F, low 51 °F 80°51° MayJune: average high 87 °F, low 56 °F 87°56° JunJuly: average high 94 °F, low 62 °F 94°62° JulAugust: average high 95 °F, low 62 °F 95°62° AugSeptember: average high 92 °F, low 59 °F 92°59° SepOctober: average high 82 °F, low 49 °F 82°49° OctNovember: average high 72 °F, low 41 °F 72°41° NovDecember: average high 65 °F, low 37 °F 65°37° Dec

Precipitation by month inches

0″1″2″3″January: 2.05 in precipitation 2.0 JanFebruary: 2.43 in precipitation 2.4 FebMarch: 1.51 in precipitation 1.5 MarApril: 0.76 in precipitation 0.8 AprMay: 0.27 in precipitation 0.3 MayJune: 0.07 in precipitation 0.1 JunJuly: 0.13 in precipitation 0.1 JulAugust: 0.36 in precipitation 0.4 AugSeptember: 0.16 in precipitation 0.2 SepOctober: 0.47 in precipitation 0.5 OctNovember: 0.67 in precipitation 0.7 NovDecember: 1.77 in precipitation 1.8 Dec

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: March AFB, CA (4 mi away); precipitation: March AFB, CA (4 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

6 of the 8 nearest ZIP codes are in a different zone — elevation and distance from water change winter lows quickly.

925189b
March Air Reserve Base, CA · 3 mi
9250610a
Riverside, CA · 4 mi
9250410a
Riverside, CA · 4 mi
925539b
Moreno Valley, CA · 5 mi
9252110a
Riverside, CA · 5 mi
9250210a
Riverside, CA · 6 mi
9251310a
Riverside, CA · 6 mi
9251410a
Riverside, CA · 6 mi

All 16 ZIP codes in Riverside → · California planting zones →

Questions about 92508

What planting zone is ZIP code 92508?

ZIP code 92508 (Riverside, 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).

How much rain and snow does 92508 get?

About 10.7 inches of precipitation a year (NOAA 1991–2020 normals, March AFB station).

How hot do summers get in Riverside, CA?

The average high peaks at 95 °F in August, with about 100 days a year at 90 °F or more.

What kind of soil does 92508 have?

The USDA soil survey maps Fallbrook at the center of ZIP 92508: sandy loam, well drained, pH about 6.5 (neutral).

Did spring come early in Riverside, CA in 2026?

Spring leaf-out near 92508 came on Jan 18 in 2026, 6 days earlier than the 1991–2020 average (Jan 24), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Riverside, CA?

Intermediate onions: the longest day near 92508 is 14 h 25 min, so day-neutral types bulb best; long-day varieties may not bulb fully.