Weather StoryAlmanac, microseasons, and the day's weather story.

Ontario, California Weather

Summer heat deepens across the valleys. Day 15 of summer. Read this microseason across nine climate regions →

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

Ontario, CA
Sunday, July 5 at 12:02 PM
87
°
Clear
Feels like
91°
Humidity
42%
Wind
7 mph
Sunrise
10:44 PM
Sunset
1:05 PM
Ontario, CA
Hour by hour · 24h
24-Hour ForecastOntario, CA: 24-hour forecast. Temperatures range from 60 to 91 degrees Fahrenheit.
L 60°H 91°
Ontario, CA
7-day forecast
  1. Today
    Jul 5
    Overcast
    —
    —
    91°66°—
  2. Monday
    Jul 6
    Clear
    —
    —
    91°60°0°
  3. Tuesday
    Jul 7
    Clear
    —
    —
    93°64°+2°
  4. Wednesday
    Jul 8
    Clear
    —
    —
    97°74°+4°
  5. Thursday
    Jul 9
    Clear
    —
    —
    98°77°+1°
  6. Friday
    Jul 10
    Overcast
    —
    —
    95°76°-3°
  7. Saturday
    Jul 11
    Overcast
    —
    —
    91°74°-4°
Ontario, CA
Next 24 hours · Warm now
HOT 90°50°75°100°6a12p6p12anow 87°high 91°low 60°
Ontario, CA
Anemometer · 24h winds · from true
NESW
From · True
W
259° · veering 12°
Direction
W
259°
Sustained
7
mph
Gust
9
mph
Peak 24h
17
avg 6
Beaufort · 2 · LIGHT BRZ
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 6 · pk 17 @ 9:00p
01020MPHB1B2B3B4B5-21h-18h-15h-12h-9h-6h-3h-24hNOWpk 186SUSTGUST
−24h−18h−12h−6hnow
A whisper of wind — leaves barely shift on the trees.
Ontario, CA
Barometer · 24h pressure · mb
STORMRAINCHANGEFAIRDRY9901000101010201030
Pressure · mb
983.5
-0.1 mb in 3h · steady · 29.04 inHg
Now
983.5
mb
3h
-0.1
mb
12h
+0.1
mb
24h
-1.8
mb
Regime · STORM
STORM
RAIN
CHANGE
FAIR
DRY
24h · Pressure · mb
range 982–985
975980985990-21h-18h-15h-12h-9h-6h-3h-24hNOW985.3982.4983.5
−24h−18h−12h−6hnow
Deep low — expect rough seas, strong wind, and persistent rain.
Ontario, CA
Air quality
50
AQI
Good
→0 in 6h

AQI 50 (Good), driven by PM2.5. AQI flat over the last 6 hours (within ±3 points). PM2.5 at 13.4 µg/m³, PM10 at 17.8 µg/m³ — typical background levels with no transport signature.

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

PM 2.5DRIVERModerate
13.4μg/m³
PM 10Good
18μg/m³
NO₂Good
5μg/m³
OzoneModerate
98μg/m³
UV IndexExtreme
12.2

What's driving it

Ozone × UV × Sky

Ozone at AQI 46 now. With UV 12 peaking around 1 PM under clear skies, surface ozone likely climbs to AQI 74 around 1 PM.

Present
AQI 46
UV peak
12.0 at 1 PM
Sky at peak
clear
Projected peak
AQI 74

PM × Wind × Precip

PM2.5 at 13.4 µg/m³, PM10 at 17.8 µg/m³ — typical background levels with no transport signature.

PM2.5/PM10
0.75
Wind
light
Recent rain
0h in last 6h
Pattern
background

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/m³360
Ontario, CA
Sky cover · visibility · 24h
Cloud cover
3%
CLEAR
100%0%−24h−18h−12h−6hnow
Visibility
90.3mi
UNLIMITED
164 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
19:02 UTC · Ontario, 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
19:02 UTC · Ontario, CA · NOAA NESDIS / STAR · 5-min cadence · up to 10000 px
Ontario, CA
Satellite · infrared · animated
Ontario, CA
Loading IR frames…
IR · cloud-top temp© RainViewer · Carto
Ontario, CA
Almanac · Sunday, July 5
If the first of July be rainy weather, 'twill rain more or less for four weeks together.
Civil dawn
5:16 AM
Sunrise
10:44 PM
Daylight
14h 21m
Sunset
1:05 PM
Civil dusk
8:35 PM
Planting note
Harvest early potatoes. Begin drying onions on the surface.
Ontario, CA
The moon
Waning Gibbous
70% illuminated
Moonrise
11:06 PM
Moonset
11:09 AM
In sign
♓︎ Pisces
Ontario, CA
Microseason
Jul 1–5

Summer heat deepens across the valleys

weather
Jan 151% of the yearDec 31

Read this microseason across nine climate regions →

Ontario at a glance

  • Today vs. normal: 9°F above the seasonal normal for this latitude
  • Last frost: March 11 (climatological average for this latitude)
  • Microseason: Jul 1–5
  • Planting window: Harvest early potatoes. Begin drying onions on the surface.

ZIP codes: 91761, 91762, 91764

16-Day Forecast — Ontario

  1. Sun91°66°1%
  2. Mon91°60°1%
  3. Tue93°64°0%
  4. Wed97°74°0%
  5. Thu98°77°0%
  6. Fri95°76°0%
  7. Sat91°74°1%
  8. Sun88°73°1%
  9. Mon100°76°6%
  10. Tue103°82°12%
  11. Wed101°83°6%
  12. Thu104°83°19%
  13. Fri103°85°19%
  14. Sat98°83°9%
  15. Sun102°83°10%
  16. Mon103°82°6%

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

Live wind & temperature near Ontario

Right now in the garden

Peak growing season

As of July 5, 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.

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 · July 1–5

Summer heat deepens across the valleys

Inland temperatures exceed 95°F regularly; fire danger reaches moderate to high across most of the region.

Day 186 of 365 · Wedge 37 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

Ontario's warmest month is August (~80°F mean) and its coldest is January (~52°F). Rainfall peaks in February (3.4 inches) and bottoms out in August (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

Per NOAA NCEI 1991-2020 normals, Ontario runs from a 52°F January mean to 79°F in July, a 27°F seasonal spread, with near 16.7 inches of precipitation across about 82 wet days.

Cool-season fronts carry Ontario's rain: February logs 3.4 inches on 9.9 days, against August's 0.0 inches on 0.9 — winter does the heavy lifting in Ontario. That groups Ontario with places like Chino, CA, Eastvale, CA and Montclair, CA on the same cool-season storm track.

Hard freezes are rare in Ontario: the coldest month averages 52°F, so Ontario's growing window runs most of the year. August is the hottest stretch near 80°F, pushing cool-season crops to the milder shoulder months. Ontario's coastal lots stay 4-7°F milder overnight than Ontario's inland parcels.

Similar climates: Chino, CA, Eastvale, CA, Montclair, CA, Upland, CA, Rancho Cucamonga, CA.

Naturalist notes

Late May brings the peak migration of Yellow Warblers through Ontario's parks and green spaces.

Coastal live oaks begin dropping their acorns in September as temperatures start their gradual decline.

Frequently asked

When does it freeze in Ontario?
Frost typically leaves Ontario by mid-March and returns to Ontario near mid-December.
What is the rainy season in Ontario?
Rainfall in Ontario peaks in February near 3.4 inches, out of about 17 inches annually.
What is the warmest month in Ontario?
August is Ontario's warmest month, averaging about 80°F.
What is the coldest month in Ontario?
Ontario bottoms out in January, with a mean near 52°F.
When can I start a vegetable garden in Ontario?
Ontario's last frost (mid-March) cues hardy greens; in Ontario, hold heat-lovers two weeks past.
How many rainy days does Ontario get?
Ontario records around 82 days of measurable precipitation annually.
What hardiness zone is Ontario?
Ontario sits in the USDA zone set by January lows near 52°F; the USDA ZIP tool gives the band.
What is the 10-day forecast for Ontario?
Ontario'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 Ontario?
See this week's day-by-day rain chances for Ontario in the daily forecast above, and the next 24 hours in the hourly chart.
What is the weather like right now in Ontario?
Current conditions for Ontario and the next 24 hours — temperature, precipitation chance, and wind by the hour — are in the hourly forecast chart above.
How often is the Ontario forecast updated?
The Ontario forecast on this page is built from Open-Meteo weather-model data and refreshes regularly through the day.
When are sunrise and sunset in Ontario?
Today's sunrise and sunset times for Ontario 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 Ontario?
The next few days in Ontario's forecast are the most reliable; accuracy declines beyond about a week as weather-model uncertainty grows.

Climate

Ontario, California occupies a hot-summer Mediterranean zone, with January means near 52°F and July around 79°F — a 27°F swing.

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

The 27°F gap between Ontario's summer and winter, at 34.0°N, shapes Ontario's frost calendar.

All cities in California →

Riverside, CA weather →

ZIP codes in Ontario

  • 91762
  • 91761
  • 91764
  • 91743
  • 91758

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.