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Castro Valley, California Weather

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

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

Castro Valley, CA
Sunday, July 5 at 10:56 AM
61
°
Partly Cloudy
Feels like
60°
Humidity
79%
Wind
4 mph
Sunrise
10:52 PM
Sunset
1:33 PM
Castro Valley, CA
Hour by hour · 24h
24-Hour ForecastCastro Valley, CA: 24-hour forecast. Temperatures range from 54 to 70 degrees Fahrenheit.
L 54°H 70°
Castro Valley, CA
7-day forecast
  1. Today
    Jul 5
    Foggy
    —
    —
    70°55°—
  2. Monday
    Jul 6
    Foggy
    —
    —
    66°54°-4°
  3. Tuesday
    Jul 7
    Foggy
    —
    —
    68°53°+2°
  4. Wednesday
    Jul 8
    Overcast
    —
    —
    74°56°+6°
  5. Thursday
    Jul 9
    Clear
    —
    —
    74°57°0°
  6. Friday
    Jul 10
    Overcast
    —
    —
    78°57°+4°
  7. Saturday
    Jul 11
    Overcast
    —
    —
    81°62°+3°
Castro Valley, CA
Next 24 hours · Cool now
50°62°74°6a12p6p12anow 59°high 70°low 54°
Castro Valley, CA
Anemometer · 24h winds · from true
NESW
From · True
W
273° · steady
Direction
W
273°
Sustained
4
mph
Gust
6
mph
Peak 24h
11
avg 7
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 7 · pk 11 @ 4:00p
01020MPHB1B2B3B4B5-21h-18h-15h-12h-9h-6h-3h-24hNOWpk 147SUSTGUST
−24h−18h−12h−6hnow
A whisper of wind — leaves barely shift on the trees.
Castro Valley, CA
Barometer · 24h pressure · mb
STORMRAINCHANGEFAIRDRY9901000101010201030
Pressure · mb
1003.7
+0.4 mb in 3h · steady · 29.64 inHg
Now
1003.7
mb
3h
+0.4
mb
12h
+0.2
mb
24h
-0.4
mb
Regime · RAIN
STORM
RAIN
CHANGE
FAIR
DRY
24h · Pressure · mb
range 1002–1004
9951000STORM|RAIN10051010RAIN|CHG1015CHG|FAIR10201025FAIR|DRY1030-21h-18h-15h-12h-9h-6h-3h-24hNOW1003.91001.81003.3
−24h−18h−12h−6hnow
Damp, unsettled regime — wet weather lingers nearby.
Castro Valley, CA
Air quality
36
AQI
Good
→-1 in 6h

AQI 36 (Good), driven by PM2.5. AQI flat over the last 6 hours (within ±3 points). PM2.5 at 8.1 µg/m³ (AQI 45) with a 0.72 fine-to-coarse ratio and 4 mph wind — combustion smoke trapped in calm air, not road dust.

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

PM 2.5DRIVERGood
8.1μg/m³
PM 10Good
11μg/m³
NO₂Good
5μg/m³
OzoneGood
55μg/m³
UV IndexModerate
4.5

What's driving it

PM × Wind × Precip

PM2.5 at 8.1 µg/m³ (AQI 45) with a 0.72 fine-to-coarse ratio and 4 mph wind — combustion smoke trapped in calm air, not road dust.

PM2.5/PM10
0.72
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
Castro Valley, CA
Sky cover · visibility · 24h
Cloud cover
75%
MOSTLY CLOUDY
100%0%−24h−18h−12h−6hnow
Visibility
35.5mi
UNLIMITED
71 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
17:56 UTC · Castro Valley, 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
17:56 UTC · Castro Valley, CA · NOAA NESDIS / STAR · 5-min cadence · up to 10000 px
Castro Valley, CA
Satellite · infrared · animated
Castro Valley, CA
Loading IR frames…
IR · cloud-top temp© RainViewer · Carto
Castro Valley, CA
Almanac · Sunday, July 5
If the first of July be rainy weather, 'twill rain more or less for four weeks together.
Civil dawn
5:22 AM
Sunrise
10:52 PM
Daylight
14h 41m
Sunset
1:33 PM
Civil dusk
9:05 PM
Planting note
Harvest early potatoes. Begin drying onions on the surface.
Castro Valley, CA
The moon
Waning Gibbous
71% illuminated
Moonrise
11:27 PM
Moonset
11:27 AM
In sign
♓︎ Pisces
Castro Valley, 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 →

Castro Valley at a glance

  • Today vs. normal: 13°F below the seasonal normal for this latitude
  • Last frost: April 2 (climatological average for this latitude)
  • Microseason: Jul 1–5
  • Planting window: Harvest early potatoes. Begin drying onions on the surface.

ZIP codes: 94546, 94552

16-Day Forecast — Castro Valley

  1. Sun70°55°1%
  2. Mon66°54°1%
  3. Tue68°53°1%
  4. Wed74°56°0%
  5. Thu74°57°0%
  6. Fri78°57°0%
  7. Sat81°62°0%
  8. Sun75°63°1%
  9. Mon85°66°3%
  10. Tue81°64°5%
  11. Wed78°62°0%
  12. Thu79°61°3%
  13. Fri83°64°0%
  14. Sat78°62°0%
  15. Sun75°61°3%
  16. Mon76°59°3%

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

Live wind & temperature near Castro Valley

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——
March——
Aprillettuce, peas, spinach, radishes—
Maylettuce, peas, spinach, radishes, tomatoes, peppers, beans, squashlettuce, peas, radishes
Junetomatoes, peppers, beans, squashlettuce, peas, radishes
Julytomatoes, peppers, beans, squashtomatoes, beans, summer squash
August—tomatoes, beans, summer squash
Septemberfall brassicas, garlic (overwinter), carrotstomatoes, beans, summer squash
Octoberfall brassicas, garlic (overwinter), carrotswinter squash, tomatoes (last)
November——
December——

A year in weather

In Castro Valley, July runs warmest near 69°F and January coldest around 49°F, while January is the wettest month (3.4 inches) and July the driest (0.0 inches).

MonthMean tempPrecipRainy days
January49°3.4″13
February51°3.3″12
March53°2.7″13
April57°1.4″9
May63°0.5″4
June67°0.0″1
July69°0.0″1
August69°0.0″1
September69°0.1″1
October64°0.5″4
November55°2.1″8
December49°3.0″12

Regional context

By the nearest station's NOAA NCEI 1991-2020 normals, Castro Valley sees 49°F Januarys and 69°F Julys, a 21°F range, plus around 17.2 inches of precipitation across 79 days.

Precipitation in Castro Valley peaks in the cool season: January averages 3.4 inches across 13.3 storm-fed days, while July bottoms out at 0.0 inches over just 0.9 rainy days. It is a winter-storm rhythm Castro Valley shares with places like Fairview, CA, Cherryland, CA and Ashland, CA.

Castro Valley rarely sees a hard freeze — its coldest month sits near 49°F — so planting spans most of the calendar. Heat peaks in July around 69°F, which confines cool-season crops to the shoulders of summer. Castro Valley's coastal lots stay 4-7°F milder overnight than Castro Valley's inland parcels.

Similar climates: Fairview, CA, Cherryland, CA, Ashland, CA, San Lorenzo, CA, Norris Canyon, CA.

Frequently asked

When does it freeze in Castro Valley?
Frost typically leaves Castro Valley by mid-April and returns to Castro Valley near mid-November.
What is the rainy season in Castro Valley?
Castro Valley sees its heaviest rain in January (around 3.4 inches), part of roughly 17 inches a year.
What is the warmest month in Castro Valley?
Castro Valley peaks in July, when the mean runs near 69°F.
What is the coldest month in Castro Valley?
January is Castro Valley's coldest month, averaging about 49°F.
When can I start a vegetable garden in Castro Valley?
In Castro Valley, sow peas and hardy greens around mid-April; Castro Valley's tomatoes and peppers wait two weeks more.
How many rainy days does Castro Valley get?
Castro Valley records around 79 days of measurable precipitation annually.
What hardiness zone is Castro Valley?
With January around 49°F, Castro Valley's zone reflects that minimum — the USDA ZIP map confirms Castro Valley's band.
What is the 10-day forecast for Castro Valley?
Castro Valley'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 Castro Valley?
See this week's day-by-day rain chances for Castro Valley in the daily forecast above, and the next 24 hours in the hourly chart.
What is the weather like right now in Castro Valley?
Current conditions for Castro Valley and the next 24 hours — temperature, precipitation chance, and wind by the hour — are in the hourly forecast chart above.
How often is the Castro Valley forecast updated?
The Castro Valley forecast on this page is built from Open-Meteo weather-model data and refreshes regularly through the day.
When are sunrise and sunset in Castro Valley?
Today's sunrise and sunset times for Castro Valley 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 Castro Valley?
The next few days in Castro Valley's forecast are the most reliable; accuracy declines beyond about a week as weather-model uncertainty grows.

Climate

In Castro Valley, California, the hot-summer Mediterranean climate runs from about 49°F in January to 69°F in July, a 20°F seasonal range.

Across the year, Castro Valley collects about 17 inches of precipitation over roughly 79 days with measurable rain or snow.

From 37.7°N, Castro Valley sees a 20°F seasonal swing that governs Castro Valley's planting and frost windows.

All cities in California →

Oakland, CA weather →

ZIP codes in Castro Valley

  • 94546
  • 94552
  • 94578

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.