National Oceanic and Atmospheric Administration National Weather Service United States Department of Commerce

Atmospheric River Bringing Heavy Rain to Southern California and Heavy Snow to the Sierra Nevadas

A strong atmospheric river will continue heavy rain over southern California through Friday. The heaviest rainfall is ongoing today in the Los Angeles Basin. Flash and urban flooding is possible. A prolonged heavy snowfall has begun over the Sierra Nevada Mountains and will continue through Friday. Travel will become increasingly difficult over the passes due to snow and strong winds. Read More >

Hazardous Weather Conditions

Current conditions at

Hayward, Hayward Air Terminal (KHWD)

Lat: 37.66083°NLon: 122.11833°WElev: 46.0ft.

Rain

54°F

12°C

Humidity 93%
Wind Speed SSE 11 MPH
Barometer 29.65 in (1004.06 mb)
Dewpoint 52°F (11°C)
Visibility 10.00 mi
Last update 25 Dec 04:20 AM PST
Extended Forecast for

Castro Valley CA

Flood Watch December 25, 04:39am until December 26, 10:00pm
Wind Advisory December 25, 04:39am until December 25, 10:00am
Flood Advisory until December 25, 05:45am
Click here for hazard details and duration
Flood Watch
Wind Advisory
Flood Advisory
  •  
    Flood Watch December 25, 04:39am until December 26, 10:00pm
    Wind Advisory December 25, 04:39am until December 25, 10:00am
    Flood Advisory until December 25, 05:45am

    NOW: Multiple hazards in effect

    Click HERE for Details

  • Overnight

    Low: 52 °F

    Severe
    Thunderstorms

  • Christmas Day

    Christmas Day: Rain and possibly a thunderstorm before 10am, then showers and possibly a thunderstorm between 10am and 4pm, then rain after 4pm. Some of the storms could be severe. High near 57. South wind 16 to 18 mph, with gusts as high as 33 mph. Chance of precipitation is 100%. New rainfall amounts between a quarter and half of an inch possible.

    High: 57 °F

    Severe
    Thunderstorms

  • Thursday Night

    Thursday Night: Rain before 7pm, then showers and possibly a thunderstorm between 7pm and 10pm, then rain likely after 10pm. Some of the storms could be severe. Low around 49. South wind 14 to 18 mph, with gusts as high as 32 mph. Chance of precipitation is 100%. New precipitation amounts between a quarter and half of an inch possible.

    Low: 49 °F

    Severe
    Thunderstorms
    then Rain
    Likely

  • Friday

    Friday: Rain. High near 56. South wind 10 to 13 mph, with gusts as high as 25 mph. Chance of precipitation is 90%. New precipitation amounts between a tenth and quarter of an inch possible.

    High: 56 °F

    Rain

  • Friday Night

    Friday Night: A 50 percent chance of rain. Mostly cloudy, with a low around 45. South southwest wind around 6 mph. New precipitation amounts of less than a tenth of an inch possible.

    Low: 45 °F

    Chance Rain

  • Saturday

    Saturday: A 20 percent chance of rain. Partly sunny, with a high near 54.

    High: 54 °F

    Slight Chance
    Rain

  • Saturday Night

    Saturday Night: Mostly clear, with a low around 38.

    Low: 38 °F

    Mostly Clear

  • Sunday

    Sunday: Sunny, with a high near 53.

    High: 53 °F

    Sunny

Detailed Forecast

Overnight
Showers and possibly a thunderstorm. Some of the storms could be severe. Low around 52. South wind around 21 mph, with gusts as high as 38 mph. Chance of precipitation is 90%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.
Christmas Day
Rain and possibly a thunderstorm before 10am, then showers and possibly a thunderstorm between 10am and 4pm, then rain after 4pm. Some of the storms could be severe. High near 57. South wind 16 to 18 mph, with gusts as high as 33 mph. Chance of precipitation is 100%. New rainfall amounts between a quarter and half of an inch possible.
Thursday Night
Rain before 7pm, then showers and possibly a thunderstorm between 7pm and 10pm, then rain likely after 10pm. Some of the storms could be severe. Low around 49. South wind 14 to 18 mph, with gusts as high as 32 mph. Chance of precipitation is 100%. New precipitation amounts between a quarter and half of an inch possible.
Friday
Rain. High near 56. South wind 10 to 13 mph, with gusts as high as 25 mph. Chance of precipitation is 90%. New precipitation amounts between a tenth and quarter of an inch possible.
Friday Night
A 50 percent chance of rain. Mostly cloudy, with a low around 45. South southwest wind around 6 mph. New precipitation amounts of less than a tenth of an inch possible.
Saturday
A 20 percent chance of rain. Partly sunny, with a high near 54.
Saturday Night
Mostly clear, with a low around 38.
Sunday
Sunny, with a high near 53.
Sunday Night
Patchy frost after 3am. Otherwise, mostly clear, with a low around 37.
Monday
Areas of frost before 8am. Otherwise, sunny, with a high near 55.
Monday Night
Patchy frost. Otherwise, mostly clear, with a low around 37.
Tuesday
Patchy frost. Otherwise, sunny, with a high near 57.
Tuesday Night
Partly cloudy, with a low around 39.
Wednesday
Mostly cloudy, with a high near 58.
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ABOUT THIS FORECAST

 
Point Forecast:
Castro Valley CA
 37.71°N 122.08°W (Elev. 397 ft)
Last Update:
12:27 am PST Dec 25, 2025
Forecast Valid:
4am PST Dec 25, 2025-6pm PST Dec 31, 2025
 
Forecast Discussion
 
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Additional Resources

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Hourly Weather Forecast

National Digital Forecast Database

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High Temperature

National Digital Forecast Database Weather Element Forecast

Chance of Precipitation