Current Conditions

Castro Valley, California

77°F25°C

Partly Cloudy

Wind

W 4 mph7 km/h

Humidity

44%

Cloud Cover

84%

As of Tuesday, September 8, 2026 at 9:19 PM PDT

Today's Outlook

Night

Mostly cloudy, with a low around 67°F19°C. Light wind from the WSW around 3 mph5 km/h.

7-Day Forecast

Condition	High (°F)	Low (°F)	Precip (mm)	Cloud Cover (%)	Wind (mph)
Partly Cloudy	High 94°F34°C	Low 67°F19°C	Precip 0 in0 mm—	Cloud 70%	Wind NW 4 mph6 km/h	Wednesday: Mostly cloudy and hot, with a high of 94°F34°C and morning low of 69°F21°C. Light wind from the N around 4 mph7 km/h. Dry air. Wednesday Night: Mostly cloudy, with a low around 67°F19°C. Light wind from the WSW around 3 mph5 km/h.
Clear	High 89°F32°C	Low 68°F20°C	Precip 0 in0 mm—	Cloud 24%	Wind WSW 5 mph8 km/h	Thursday: Partly cloudy and hot, with a high of 89°F32°C and morning low of 71°F21°C. Breezy from the WSW at 6 to 9 mph10 to 14 km/h. Thursday Night: Mostly clear, with a low around 68°F20°C. Light wind from the SW around 4 mph7 km/h.
Clear	High 78°F26°C	Low 61°F16°C	Precip 0 in0 mm—	Cloud 16%	Wind WSW 6 mph10 km/h	Friday: Mostly clear and warm, with a high of 78°F26°C and morning low of 63°F17°C. Breezy from the WSW at 8 to 9 mph12 to 14 km/h. Friday Night: Mostly clear, with a low around 61°F16°C. Light wind from the SW around 5 mph9 km/h.
Clear	High 74°F23°C	Low 58°F14°C	Precip 0 in0 mm—	Cloud 14%	Wind WSW 8 mph13 km/h	Saturday: Mostly clear and warm, with a high of 74°F23°C and morning low of 60°F16°C. Breezy from the WSW at 9 to 11 mph15 to 18 km/h. Saturday Night: Mostly clear, with a low around 58°F14°C. Breezy from the WSW at 6 to 8 mph10 to 14 km/h.
Clear	High 77°F25°C	Low 56°F13°C	Precip 0 in0 mm—	Cloud 8%	Wind W 6 mph9 km/h	Sunday: Mostly clear and warm, with a high of 77°F25°C and morning low of 60°F15°C. Breezy from the WNW at 7 to 9 mph11 to 14 km/h. Dry air. Sunday Night: Mostly clear, with a low around 56°F13°C. Light wind from the WSW around 5 mph8 km/h.
Clear	High 79°F26°C	Low 55°F13°C	Precip 0 in0 mm—	Cloud 13%	Wind WSW 5 mph7 km/h	Monday: Mostly clear and warm, with a high of 79°F26°C and morning low of 58°F15°C. Breezy from the W at 5 to 8 mph8 to 13 km/h. Monday Night: Mostly clear, with a low around 55°F13°C. Light wind from the SW around 4 mph6 km/h.
Clear	High 76°F24°C	Low 56°F14°C	Precip 0 in0 mm—	Cloud 33%	Wind WSW 6 mph9 km/h	Tuesday: Partly cloudy and warm, with a high of 76°F24°C and morning low of 60°F15°C. Breezy from the WSW at 6 to 8 mph10 to 13 km/h. Tuesday Night: Partly cloudy, with a low around 56°F14°C. Light wind from the SW around 5 mph8 km/h.

15-Day Forecast

	Day	High	Low	Precip	Cloud Cover	Condition	Wind
	WednesdaySep 9	94°F34°C	67°F19°C	0 in0 mm· —	70%	Partly Cloudy	NW 4 mph6 km/h
DayMostly cloudy and hot, with a high of 94°F34°C and morning low of 69°F21°C. Light wind from the N around 4 mph7 km/h. Dry air. NightMostly cloudy, with a low around 67°F19°C. Light wind from the WSW around 3 mph5 km/h.
	ThursdaySep 10	89°F32°C	68°F20°C	0 in0 mm· —	24%	Clear	WSW 5 mph8 km/h
DayPartly cloudy and hot, with a high of 89°F32°C and morning low of 71°F21°C. Breezy from the WSW at 6 to 9 mph10 to 14 km/h. NightMostly clear, with a low around 68°F20°C. Light wind from the SW around 4 mph7 km/h.
	FridaySep 11	78°F26°C	61°F16°C	0 in0 mm· —	16%	Clear	WSW 6 mph10 km/h
DayMostly clear and warm, with a high of 78°F26°C and morning low of 63°F17°C. Breezy from the WSW at 8 to 9 mph12 to 14 km/h. NightMostly clear, with a low around 61°F16°C. Light wind from the SW around 5 mph9 km/h.
	SaturdaySep 12	74°F23°C	58°F14°C	0 in0 mm· —	14%	Clear	WSW 8 mph13 km/h
DayMostly clear and warm, with a high of 74°F23°C and morning low of 60°F16°C. Breezy from the WSW at 9 to 11 mph15 to 18 km/h. NightMostly clear, with a low around 58°F14°C. Breezy from the WSW at 6 to 8 mph10 to 14 km/h.
	SundaySep 13	77°F25°C	56°F13°C	0 in0 mm· —	8%	Clear	W 6 mph9 km/h
DayMostly clear and warm, with a high of 77°F25°C and morning low of 60°F15°C. Breezy from the WNW at 7 to 9 mph11 to 14 km/h. Dry air. NightMostly clear, with a low around 56°F13°C. Light wind from the WSW around 5 mph8 km/h.
	MondaySep 14	79°F26°C	55°F13°C	0 in0 mm· —	13%	Clear	WSW 5 mph7 km/h
DayMostly clear and warm, with a high of 79°F26°C and morning low of 58°F15°C. Breezy from the W at 5 to 8 mph8 to 13 km/h. NightMostly clear, with a low around 55°F13°C. Light wind from the SW around 4 mph6 km/h.
	TuesdaySep 15	76°F24°C	56°F14°C	0 in0 mm· —	33%	Clear	WSW 6 mph9 km/h
DayPartly cloudy and warm, with a high of 76°F24°C and morning low of 60°F15°C. Breezy from the WSW at 6 to 8 mph10 to 13 km/h. NightPartly cloudy, with a low around 56°F14°C. Light wind from the SW around 5 mph8 km/h.
	WednesdaySep 16	75°F24°C	57°F14°C	0 in0 mm· —	32%	Clear	WSW 5 mph9 km/h
DayPartly cloudy and warm, with a high of 75°F24°C and morning low of 59°F15°C. Breezy from the WSW at 6 to 8 mph10 to 12 km/h. NightPartly cloudy, with a low around 57°F14°C. Light wind from the SW around 5 mph8 km/h.
	ThursdaySep 17	77°F25°C	56°F14°C	0 in0 mm· —	26%	Clear	WSW 5 mph8 km/h
DayMostly clear and warm, with a high of 77°F25°C and morning low of 59°F15°C. Breezy from the W at 5 to 7 mph9 to 12 km/h. NightPartly cloudy, with a low around 56°F14°C. Light wind from the WSW around 4 mph7 km/h.
	FridaySep 18	76°F25°C	57°F14°C	0 in0 mm· —	32%	Clear	WSW 5 mph8 km/h
DayPartly cloudy and warm, with a high of 76°F25°C and morning low of 59°F15°C. Breezy from the W at 5 to 7 mph9 to 12 km/h. NightPartly cloudy, with a low around 57°F14°C. Light wind from the WSW around 4 mph7 km/h.
	SaturdaySep 19	76°F25°C	57°F14°C	0.01 in0.3 mm· 3%	40%	Clear	WSW 5 mph8 km/h
DayPartly cloudy and warm, with a high of 76°F25°C and morning low of 59°F15°C. Breezy from the W at 6 to 8 mph9 to 13 km/h. NightPartly cloudy, with a low around 57°F14°C. Light wind from the WSW around 4 mph7 km/h.
	SundaySep 20	75°F24°C	58°F14°C	0 in0.1 mm· 2%	38%	Clear	WSW 6 mph9 km/h
DayPartly cloudy and warm, with a high of 75°F24°C and morning low of 59°F15°C. Breezy from the W at 6 to 8 mph10 to 13 km/h. NightPartly cloudy, with a low around 58°F14°C. Light wind from the SW around 5 mph8 km/h.
	MondaySep 21	76°F24°C	58°F14°C	0.01 in0.2 mm· 2%	36%	Clear	WSW 5 mph8 km/h
DayPartly cloudy and warm, with a high of 76°F24°C and morning low of 59°F15°C. Breezy from the WSW at 6 to 8 mph9 to 12 km/h. NightPartly cloudy, with a low around 58°F14°C. Light wind from the SW around 5 mph8 km/h.
	TuesdaySep 22	78°F26°C	58°F15°C	0.01 in0.2 mm· 4%	33%	Clear	WSW 5 mph8 km/h
DayPartly cloudy and warm, with a high of 78°F26°C and morning low of 61°F16°C. Breezy from the W at 6 to 7 mph9 to 12 km/h. NightPartly cloudy, with a low around 58°F15°C. Light wind from the SW around 4 mph7 km/h.
	WednesdaySep 23	79°F26°C	59°F15°C	0.01 in0.2 mm· 5%	31%	Clear	WSW 5 mph8 km/h
DayPartly cloudy and warm, with a high of 79°F26°C and morning low of 61°F16°C. Breezy from the W at 5 to 7 mph9 to 12 km/h. NightPartly cloudy, with a low around 59°F15°C. Light wind from the SW around 4 mph6 km/h.

Nearby Cities

Ashland2 mi2 km Hayward2 mi3 km San Lorenzo3 mi5 km San Leandro4 mi7 km Union City8 mi12 km Dublin8 mi13 km

About This Forecast

This forecast is powered by WeatherMesh, the world's most advanced and accurate weather model powered by AI. WeatherMesh is built on proprietary data from WindBorne's Global Sounding Balloon constellation — the world's largest fleet of autonomous, long-duration weather balloons — collecting observations across 100% of Earth, including over oceans and remote regions where no other data exists.

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Coordinates: 37.6941°N, 122.0863°W·Elevation: 50m·Timezone: America/Los_Angeles·Population: 61,388