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Rancho Cucamonga, California Weather

August begins in scorching stillness. Day 43 of summer. Read this microseason across nine climate regions →

Rancho Cucamonga weather forecast — hour by hour, 7-day outlook, NOAA radar

Rancho Cucamonga, CA
Sunday, August 2 at 7:59 AM
76
°
Clear
Feels like
79°
Humidity
60%
Wind
1 mph
Sunrise
11:02 PM
Sunset
12:50 PM
Rancho Cucamonga, CA
Hour by hour · 24h
24-Hour ForecastRancho Cucamonga, CA: 24-hour forecast. Temperatures range from 67 to 100 degrees Fahrenheit.
L 67°H 100°
Rancho Cucamonga, CA
7-day forecast
  1. Today
    Aug 2
    Clear
    —
    —
    100°68°—
  2. Monday
    Aug 3
    Clear
    —
    —
    98°67°-2°
  3. Tuesday
    Aug 4
    Clear
    —
    —
    99°68°+1°
  4. Wednesday
    Aug 5
    Clear
    —
    —
    98°80°-1°
  5. Thursday
    Aug 6
    Clear
    —
    —
    99°80°+1°
  6. Friday
    Aug 7
    Clear
    —
    —
    99°79°0°
  7. Saturday
    Aug 8
    Clear
    —
    —
    99°79°0°
Rancho Cucamonga, CA
Next 24 hours · Mild now
HOT 90°60°85°110°12p6p12a6anow 69°high 100°low 67°
Rancho Cucamonga, CA
Anemometer · 24h winds · from true
NESW
From · True
S
180° · veering 90°
Direction
S
180°
Sustained
1
mph
Gust
3
mph
Peak 24h
17
avg 5 mph
Beaufort · 1 · LIGHT AIR
0
CALM
<1
1
LIGHT AIR
1–3
2
LIGHT BRZ
4–7
3
GENTLE BRZ
8–12
4
MOD BRZ
13–18
5
FRESH BRZ
19–24
6
STRONG BRZ
25–31
7
NEAR GALE
32–38
24h · sust vs gust · mph
avg 5 mph · pk 17 mph @ 6:00p
01020MPHB1B2B3B4B5-21h-18h-15h-12h-9h-6h-3h-24hNOWpk 182SUSTGUST
−24h−18h−12h−6hnow
A whisper of wind — leaves barely shift on the trees.
Rancho Cucamonga, CA
Barometer · 24h pressure · mb
STORMRAINCHANGEFAIRDRY9901000101010201030
Pressure · mb
962.7
-0.2 mb in 3h · steady · 28.43 inHg
Now
962.7
mb
3h
-0.2
mb
12h
-1.6
mb
24h
-3.4
mb
Regime · STORM
STORM
RAIN
CHANGE
FAIR
DRY
24h · Pressure · mb
range 962–967
955960965970975-21h-18h-15h-12h-9h-6h-3h-24hNOW966.8961.6961.7
Deep low — expect rough seas, strong wind, and persistent rain.
Rancho Cucamonga, CA
Air quality
65
AQI
Moderate
→-1 in 6h

AQI 65 (Moderate), driven by PM2.5. AQI flat over the last 6 hours (within ±3 points). PM2.5 at 21.2 µg/m³ (AQI 74) with a 0.85 fine-to-coarse ratio and 1 mph wind — combustion smoke trapped in stagnant air, not road dust.

OK No precautions needed for the general population; unusually sensitive individuals may consider limiting prolonged outdoor exertion.

PM 2.5DRIVERModerate
21.2μg/m³
PM 10Good
25μg/m³
NO₂Moderate
34μg/m³
OzoneGood
32μg/m³
UV IndexLow
0.3

What's driving it

PM × Wind × Precip

PM2.5 at 21.2 µg/m³ (AQI 74) with a 0.85 fine-to-coarse ratio and 1 mph wind — combustion smoke trapped in stagnant air, not road dust.

PM2.5/PM10
0.85
Wind
calm
Recent rain
0h in last 6h
Pattern
stagnant smoke

Trends

Seven days of AQI and PM2.5.

Hourly air-quality data from the Copernicus Atmosphere Monitoring Service, charted across the past and next several days. Dashed lines mark the AQI breakpoints at 50 (Good → Moderate) and 100 (Moderate → Unhealthy for Sensitive Groups).

7-DAY AQI TREND50100SUNMONTUEWEDTHUFRISATSUN7-DAY PM2.5 TREND · μg/m³300
Rancho Cucamonga, CA
Sky cover · visibility · 24h
Cloud cover
0%
CLEAR
100%0%−24h−18h−12h−6hnow
Visibility
69.9mi
UNLIMITED
162 mi0 mi−24h−18h−12h−6hnow
Earth · GOES-19 ABI
Full Disk · Visible · GeoColor
GOES-19 full disk Visible · GeoColor
True-color daytime, blue/IR sandwich at night
14:59 UTC · Rancho Cucamonga, CA · NOAA NESDIS / STAR · up to 10848 px
Continental US · GOES-19 ABI
CONUS Sector · Visible · GeoColor
GOES-19 CONUS Visible · GeoColor
Daytime true-color, blue-light/IR sandwich at night
14:59 UTC · Rancho Cucamonga, CA · NOAA NESDIS / STAR · 5-min cadence · up to 10000 px
Rancho Cucamonga, CA
Satellite · infrared · animated
Rancho Cucamonga, CA
Loading IR frames…
IR · cloud-top temp© RainViewer · Carto
Rancho Cucamonga, CA
Almanac · Sunday, August 2
Red sky at night, sailor's delight.
Civil dawn
5:36 AM
Sunrise
11:02 PM
Daylight
13h 48m
Sunset
12:50 PM
Civil dusk
8:19 PM
Planting note
Sow fall peas. Start kale and collard seedlings for fall.
Rancho Cucamonga, CA
The moon
Waning Gibbous
84% illuminated
Moonrise
9:35 PM
Moonset
10:00 AM
In sign
♓︎ Pisces
Rancho Cucamonga, CA
Microseason
Aug 1–5

August begins in scorching stillness

plant
Jan 159% of the yearDec 31

Read this microseason across nine climate regions →

Rancho Cucamonga at a glance

  • Today vs. normal: 8°F above the seasonal normal for this latitude
  • Last frost: March 12 (climatological average for this latitude)
  • Microseason: Aug 1–5
  • Planting window: Sow fall peas. Start kale and collard seedlings for fall.

ZIP codes: 91701, 91730, 91737, 91739

16-Day Forecast — Rancho Cucamonga

  1. Sun100°68°0%
  2. Mon98°67°0%
  3. Tue99°68°0%
  4. Wed98°80°0%
  5. Thu99°80°1%
  6. Fri99°79°1%
  7. Sat99°79°2%
  8. Sun95°77°2%
  9. Mon93°75°1%
  10. Tue93°74°1%
  11. Wed93°75°1%
  12. Thu95°74°3%
  13. Fri96°77°17%
  14. Sat93°77°12%
  15. Sun97°78°3%
  16. Mon97°78°10%

Forecast data from Open-Meteo (CC BY 4.0).

Live wind & temperature near Rancho Cucamonga

Right now in the garden

Peak growing season

As of August 2, the growing season is at its peak — frost is months away. Continue succession-planting beans and summer squash. Start fall brassicas (broccoli, cabbage, kale) from seed indoors for transplanting in late summer.

Sun & seasons in Rancho Cucamonga

Rancho Cucamonga sits in San Bernardino County, where the year’s longest day runs 14h 26m of daylight and its shortest just 9h 52m — a swing of +4h 33m between the June and December solstices. Clocks spring forward on Sunday, March 8, 2026 and fall back on Sunday, November 1, 2026.

Los Angeles, the state’s largest city, lies about 48 miles to the W. The nearest town Rancho Cucamonga tracks is Ontario, roughly 6 miles to the SSW.

Air quality in Rancho Cucamonga’s county has trended cleaner since 2020; its cleanest year on record was 2023 (median AQI 71). See the full air-quality history for Rancho Cucamonga.

January 1–5: New year in coastal mist.January 6–10: Hills hold the winter cold.January 11–15: Light lengthens over wet earth.January 16–20: The green pulse quickens.January 21–25: Spring green spreads inland.January 26–31: Winter's grip releases.February 1–5: Fog lifts, flowers open.February 6–10: Blooms erupt across chaparral.February 11–15: Winter blooms at their peak.February 16–20: Rivers recede, flowers spread.February 21–25: Earth warms, flowers rush upslope.February 26–28: Spring advances on cool winds.March 1–5: Grass and trees bud and break.March 6–10: Insects wake and feed.March 11–15: Blossoms crown the hillsides.March 16–20: Monarch chrysalis emergence.March 21–25: Light overtakes dark at equinox.March 26–31: California poppy ablaze.April 1–5: Spring rain feeds the seedlings.April 6–10: Warblers flood the understory.April 11–15: Allen's hummingbirds in courtship dives.April 16–20: Coastal fog settles; sun breaks midday.April 21–25: Oak canopies full and green.April 26–30: Chaparral awakens after spring rains.May 1–5: Coastal wildflowers at their peak.May 6–10: Gray whales complete their migration north.May 11–15: Redwood coast in cool shade.May 16–20: Fog and sun in daily rhythm.May 21–25: Summer approaches; hills turn gold.May 26–31: Dry season begins; tule fog in valleys.June 1–5: Coastal fog thickens at dawn.June 6–10: California poppies fade as heat rises.June 11–15: Summer solstice light stretched thin.June 16–20: Bay laurel fragrance sweetens shade.June 21–25: Longest daylight, driest air.June 26–30: Fog banks mask the turning tide.July 1–5: Summer heat deepens across the valleys.July 6–10: Warm winds drive dryness inland.July 11–15: Pacific high settles in firmly.July 16–20: Young hawks take to the thermals.July 21–25: Peak fire season, peak heat.July 26–31: Chaparral poised for ignition.August 1–5: August begins in scorching stillness.August 6–10: Autumn's first cool breath arrives.August 11–15: Cool winds signal the turning year.August 16–20: Evening cicada chorus.August 21–25: Marine layer descent.August 26–31: Monarch staging begins.September 1–5: Fire season intensity.September 6–10: Dew on drying grasses.September 11–15: Raptor passage begins.September 16–20: Equinox descent.September 21–25: Ceanothus blooms again.September 26–30: Insects retreat below.October 1–5: Creeks begin to whisper.October 6–10: Santa Ana wind season.October 11–15: Wildflower anticipation.October 16–20: Chaparral embers glow.October 21–25: First atmospheric river looms.October 26–31: Rains return at last.November 1–5: Coast live oak leaves turn amber.November 6–10: California lilac blooms in winter light.November 11–15: First rain greens the chaparral.November 16–20: Coastal fog thickens as storms approach.November 21–25: Thanksgiving rains swell the valleys.November 26–30: Autumn's last breath yields to winter.December 1–5: December arrives, storms accelerate.December 6–10: Winter solstice season intensifies.December 11–15: Deep winter: rivers at flood stage.December 16–20: Winter salmon runs peak in northern rivers.December 21–25: Winter solstice: the sun turns.December 26–31: Year's end in wind and rain.🌱February 14 — First skunk-cabbage spathes thaw their way up☀️March 20 — Spring equinox — day and night balance🌸April 5 — Cherry blossoms peak in the parks🐦May 10 — Warbler migration peaks along the coast✨May 25 — First fireflies scout the meadows at dusk🌞June 21 — Summer solstice — longest day🦗July 25 — Peak cicada chorus in the afternoons🌊August 18 — Warmest sea-surface temperatures of the year🍂September 22 — Autumn equinox — the slow turn❄️October 25 — First widespread frost in the suburbs🍁November 10 — Peak leaf color across the Hudson Valley🌙December 21 — Winter solstice — longest night

Microseason · August 1–5

August begins in scorching stillness

Calm days dominate early August; temperatures peak; the entire ecosystem is in survival mode.

Day 214 of 365 · Wedge 43 of 72

The solar year drawn as a wheel of 72 five-day windows. Each wedge is one microseason; the four colored arcs mark winter, spring, summer, and autumn; the small icons sit at notable phenological events. The crimson pointer creeps clockwise as the year turns.

Planting calendar

MonthPlantHarvest
January——
February——
Marchlettuce, peas, spinach, radishes—
Aprillettuce, peas, spinach, radishes, tomatoes, peppers, beans, squash—
Maytomatoes, peppers, beans, squashlettuce, peas, radishes
Junetomatoes, peppers, beans, squashlettuce, peas, radishes
July—tomatoes, beans, summer squash
August—tomatoes, beans, summer squash
September—tomatoes, beans, summer squash
Octoberfall brassicas, garlic (overwinter), carrotswinter squash, tomatoes (last)
Novemberfall brassicas, garlic (overwinter), carrots—
December——

A year in weather

Rancho Cucamonga peaks at about 80°F in August and bottoms near 52°F in January; February brings the heaviest rain (3.4 inches) and August the least (0.0 inches).

MonthMean tempPrecipRainy days
January52°3.3″11
February54°3.4″10
March57°3.0″13
April62°1.5″10
May67°0.5″7
June73°0.1″3
July79°0.1″1
August80°0.0″1
September76°0.1″2
October69°0.5″5
November59°1.6″8
December53°2.6″10

Regional context

Drawing on NOAA NCEI 1991-2020 normals, Rancho Cucamonga's January averages 52°F and July 79°F — 27°F apart — while precipitation totals roughly 16.7 inches over some 82 days.

Rancho Cucamonga's moisture rides winter storm tracks: February brings 3.4 inches over 9.9 wet days, while August sees only 0.0 inches across 0.9 days in the dry warm season. That groups Rancho Cucamonga with places like Upland, CA, San Antonio Heights, CA and Ontario, CA on the same cool-season storm track.

Rancho Cucamonga rarely sees a hard freeze — its coldest month sits near 52°F — so planting spans most of the calendar. Heat peaks in August around 80°F, which confines cool-season crops to the shoulders of summer. Across Rancho Cucamonga, elevation and tree cover drive a 4-7°F spread in Rancho Cucamonga's overnight lows.

Similar climates: Upland, CA, San Antonio Heights, CA, Ontario, CA, Fontana, CA, Montclair, CA.

Naturalist notes

California poppies typically begin their spring bloom in late March as soil temperatures warm.

Allen's hummingbirds start their northward migration through the region during April and May.

Frequently asked

When does it freeze in Rancho Cucamonga?
In Rancho Cucamonga, expect the last spring frost near mid-March; Rancho Cucamonga's first autumn frost comes around mid-December.
What is the rainy season in Rancho Cucamonga?
Rainfall in Rancho Cucamonga peaks in February near 3.4 inches, out of about 17 inches annually.
What is the warmest month in Rancho Cucamonga?
On average August tops the year in Rancho Cucamonga at about 80°F.
What is the coldest month in Rancho Cucamonga?
The coldest stretch in Rancho Cucamonga falls in January, around 52°F on average.
When can I start a vegetable garden in Rancho Cucamonga?
Around mid-March, start frost-hardy crops in Rancho Cucamonga; tomatoes and basil belong a fortnight later.
How many rainy days does Rancho Cucamonga get?
Rancho Cucamonga averages about 82 days with measurable rain or snow each year.
What hardiness zone is Rancho Cucamonga?
Since January in Rancho Cucamonga averages 52°F, Rancho Cucamonga's USDA zone follows that floor — confirm it by ZIP.
What is the 10-day forecast for Rancho Cucamonga?
Rancho Cucamonga's extended outlook — daily high and low temperatures and precipitation chances for each upcoming day — is in the daily forecast above.
Will it rain this week in Rancho Cucamonga?
See this week's day-by-day rain chances for Rancho Cucamonga in the daily forecast above, and the next 24 hours in the hourly chart.
What is the weather like right now in Rancho Cucamonga?
Current conditions for Rancho Cucamonga and the next 24 hours — temperature, precipitation chance, and wind by the hour — are in the hourly forecast chart above.
How often is the Rancho Cucamonga forecast updated?
The Rancho Cucamonga forecast on this page is built from Open-Meteo weather-model data and refreshes regularly through the day.
When are sunrise and sunset in Rancho Cucamonga?
Today's sunrise and sunset times for Rancho Cucamonga are in the Almanac section above, along with civil dawn, civil dusk, and day length. Day length is longest near the summer solstice and shortest near the winter solstice.
How accurate is the weather forecast for Rancho Cucamonga?
The next few days in Rancho Cucamonga's forecast are the most reliable; accuracy declines beyond about a week as weather-model uncertainty grows.

Climate

The hot-summer Mediterranean climate of Rancho Cucamonga, California carries typical Januarys near 52°F and Julys around 79°F — 27°F of seasonal travel.

Rancho Cucamonga sees close to 17 inches of precipitation annually, falling across some 82 wet days.

From 34.1°N, Rancho Cucamonga sees a 27°F seasonal swing that governs Rancho Cucamonga's planting and frost windows.

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Riverside, CA weather →

ZIP codes in Rancho Cucamonga

  • 91730
  • 91701
  • 91737
  • 91739
  • 91729

Climate normals from the Open-Meteo Climate API. Köppen approximation from NOAA NCEI U.S. Climate Regions. See methodology for data sources, editorial rules, and corrections. Maintainer: Brian Tighe.