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Alum Rock, California Weather

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

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

Alum Rock, CA
Sunday, July 5 at 11:12 AM
71
°
Clear
Feels like
76°
Humidity
67%
Wind
3 mph
Sunrise
10:52 PM
Sunset
1:31 PM
Alum Rock, CA
Hour by hour · 24h
24-Hour ForecastAlum Rock, CA: 24-hour forecast. Temperatures range from 54 to 79 degrees Fahrenheit.
L 54°H 79°
Alum Rock, CA
7-day forecast
  1. Today
    Jul 5
    Overcast
    —
    —
    79°57°—
  2. Monday
    Jul 6
    Overcast
    —
    —
    76°54°-3°
  3. Tuesday
    Jul 7
    Overcast
    —
    —
    85°54°+9°
  4. Wednesday
    Jul 8
    Clear
    —
    —
    90°53°+5°
  5. Thursday
    Jul 9
    Clear
    —
    —
    92°59°+2°
  6. Friday
    Jul 10
    Overcast
    —
    —
    94°60°+2°
  7. Saturday
    Jul 11
    Overcast
    —
    —
    99°66°+5°
Alum Rock, CA
Next 24 hours · Mild now
45°65°85°6a12p6p12anow 71°high 79°low 54°
Alum Rock, CA
Anemometer · 24h winds · from true
NESW
From · True
W
261° · backing 34°
Direction
W
261°
Sustained
3
mph
Gust
7
mph
Peak 24h
12
avg 5
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 · pk 12 @ 3:00p
010MPHB1B2B3B4-21h-18h-15h-12h-9h-6h-3h-24hNOWpk 113SUSTGUST
−24h−18h−12h−6hnow
Light breeze backing 34° from the w.
Alum Rock, CA
Barometer · 24h pressure · mb
STORMRAINCHANGEFAIRDRY9901000101010201030
Pressure · mb
1008.9
+0.7 mb in 3h · rising · 29.79 inHg
Now
1008.9
mb
3h
+0.7
mb
12h
+0.3
mb
24h
+0.1
mb
Regime · RAIN
STORM
RAIN
CHANGE
FAIR
DRY
24h · Pressure · mb
range 1007–1009
1000STORM|RAIN10051010RAIN|CHG1015CHG|FAIR-21h-18h-15h-12h-9h-6h-3h-24hNOW1008.91007.21008.9
−24h−18h−12h−6hnow
Damp, unsettled regime — wet weather lingers nearby.
Alum Rock, CA
Air quality
32
AQI
Good
→-1 in 6h

AQI 32 (Good), driven by PM2.5. AQI flat over the last 6 hours (within ±3 points). PM2.5 at 8.6 µg/m³ (AQI 48) with a 0.68 fine-to-coarse ratio and 3 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
8.6μg/m³
PM 10Good
13μg/m³
NO₂Good
2μg/m³
OzoneModerate
68μg/m³
UV IndexVery high
7.4

What's driving it

Ozone × UV × Sky

Ozone at AQI 32 now. With UV 8.5 peaking around 1 PM under clear skies, surface ozone likely climbs to AQI 36 around 1 PM.

Present
AQI 32
UV peak
8.5 at 1 PM
Sky at peak
clear
Projected peak
AQI 36

PM × Wind × Precip

PM2.5 at 8.6 µg/m³ (AQI 48) with a 0.68 fine-to-coarse ratio and 3 mph wind — combustion smoke trapped in calm air, not road dust.

PM2.5/PM10
0.68
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
Alum Rock, CA
Sky cover · visibility · 24h
Cloud cover
4%
CLEAR
100%0%−24h−18h−12h−6hnow
Visibility
49.1mi
UNLIMITED
93 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
18:12 UTC · Alum Rock, 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
18:12 UTC · Alum Rock, CA · NOAA NESDIS / STAR · 5-min cadence · up to 10000 px
Alum Rock, CA
Satellite · infrared · animated
Alum Rock, CA
Loading IR frames…
IR · cloud-top temp© RainViewer · Carto
Alum Rock, 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 39m
Sunset
1:31 PM
Civil dusk
9:03 PM
Planting note
Harvest early potatoes. Begin drying onions on the surface.
Alum Rock, CA
The moon
Waning Gibbous
70% illuminated
Moonrise
11:26 PM
Moonset
11:26 AM
In sign
♓︎ Pisces
Alum Rock, 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 →

Alum Rock at a glance

  • Today vs. normal: 3°F below the seasonal normal for this latitude
  • Last frost: March 31 (climatological average for this latitude)
  • Microseason: Jul 1–5
  • Planting window: Harvest early potatoes. Begin drying onions on the surface.

16-Day Forecast — Alum Rock

  1. Sun79°57°0%
  2. Mon76°54°0%
  3. Tue85°54°0%
  4. Wed90°53°0%
  5. Thu92°59°0%
  6. Fri94°60°0%
  7. Sat99°66°1%
  8. Sun88°69°1%
  9. Mon96°68°3%
  10. Tue98°66°2%
  11. Wed98°66°0%
  12. Thu98°64°3%
  13. Fri102°70°0%
  14. Sat97°68°0%
  15. Sun94°67°3%
  16. Mon93°62°3%

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

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

August is Alum Rock's warmest stretch (~73°F) and January its coldest (~51°F); precipitation crests in January at 4.2 inches and ebbs in July to 0.0 inches.

MonthMean tempPrecipRainy days
January51°4.2″14
February53°3.8″12
March55°3.4″14
April59°1.7″10
May64°0.6″7
June69°0.1″5
July73°0.0″3
August73°0.1″3
September72°0.1″3
October67°0.7″5
November58°2.5″10
December51°3.6″13

Regional context

Alum Rock swings from 51°F in January to 73°F in July (22°F) per NOAA NCEI 1991-2020 normals; precipitation in Alum Rock runs about 20.8 inches on roughly 98 measurable days.

Alum Rock's moisture rides winter storm tracks: January brings 4.2 inches over 13.8 wet days, while July sees only 0.0 inches across 2.6 days in the dry warm season. That groups Alum Rock with places like East Foothills, CA, San Jose, CA and Milpitas, CA on the same cool-season storm track.

With a coldest-month mean of 51°F, Alum Rock stays mostly frost-free and grows year-round. The August peak near 73°F is Alum Rock's real limit, pushing cool-season vegetables to spring and fall. Alum Rock's coastal lots stay 4-7°F milder overnight than Alum Rock's inland parcels.

Similar climates: East Foothills, CA, San Jose, CA, Milpitas, CA, Fruitdale, CA, Santa Clara, CA.

Frequently asked

When does it freeze in Alum Rock?
In Alum Rock, expect the last spring frost near mid-April; Alum Rock's first autumn frost comes around mid-November.
What is the rainy season in Alum Rock?
Rainfall in Alum Rock peaks in January near 4.2 inches, out of about 21 inches annually.
What is the warmest month in Alum Rock?
August is Alum Rock's warmest month, averaging about 73°F.
What is the coldest month in Alum Rock?
Alum Rock bottoms out in January, with a mean near 51°F.
When can I start a vegetable garden in Alum Rock?
Time tomatoes in Alum Rock for two weeks after mid-April; peas and greens start at Alum Rock's frost line.
How many rainy days does Alum Rock get?
Expect roughly 98 wet days a year in Alum Rock.
What hardiness zone is Alum Rock?
Alum Rock sits in the USDA zone set by January lows near 51°F; the USDA ZIP tool gives the band.
What is the 10-day forecast for Alum Rock?
Alum Rock'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 Alum Rock?
See this week's day-by-day rain chances for Alum Rock in the daily forecast above, and the next 24 hours in the hourly chart.
What is the weather like right now in Alum Rock?
Current conditions for Alum Rock and the next 24 hours — temperature, precipitation chance, and wind by the hour — are in the hourly forecast chart above.
How often is the Alum Rock forecast updated?
The Alum Rock forecast on this page is built from Open-Meteo weather-model data and refreshes regularly through the day.
When are sunrise and sunset in Alum Rock?
Today's sunrise and sunset times for Alum Rock 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 Alum Rock?
The next few days in Alum Rock's forecast are the most reliable; accuracy declines beyond about a week as weather-model uncertainty grows.

Climate

Alum Rock, California occupies a hot-summer Mediterranean zone, with January means near 51°F and July around 73°F — a 22°F swing.

In a typical year Alum Rock records about 21 inches of precipitation on around 98 days.

The 22°F gap between Alum Rock's summer and winter, at 37.4°N, shapes Alum Rock's frost calendar.

All cities in California →

San Jose, CA weather →

ZIP codes in Alum Rock

  • 95127

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.