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

Port Costa, California Weather

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

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

Port Costa, CA
Sunday, July 5 at 10:02 AM
63
°
Clear
Feels like
60°
Humidity
81%
Wind
15 mph
Sunrise
10:52 PM
Sunset
1:34 PM
Port Costa, CA
Hour by hour · 24h
24-Hour ForecastPort Costa, CA: 24-hour forecast. Temperatures range from 54 to 69 degrees Fahrenheit.
L 54°H 69°
Port Costa, CA
7-day forecast
  1. Today
    Jul 5
    Overcast
    —
    —
    69°54°—
  2. Monday
    Jul 6
    Foggy
    —
    —
    68°54°-1°
  3. Tuesday
    Jul 7
    Overcast
    —
    —
    71°53°+3°
  4. Wednesday
    Jul 8
    Mostly Clear
    —
    —
    76°56°+5°
  5. Thursday
    Jul 9
    Overcast
    —
    —
    75°58°-1°
  6. Friday
    Jul 10
    Overcast
    —
    —
    79°57°+4°
  7. Saturday
    Jul 11
    Overcast
    —
    —
    82°60°+3°
Port Costa, CA
Next 24 hours · Cool now
50°61°72°6a12p6p12anow 63°high 69°low 54°
Port Costa, CA
Anemometer · 24h winds · from true
NESW
From · True
WSW
258° · backing 27°
Direction
WSW
258°
Sustained
15
mph
Gust
20
mph
Peak 24h
29
avg 13
Beaufort · 4 · MOD 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 13 · pk 29 @ 2:00a
0102030MPHB1B2B3B4B5B6-21h-18h-15h-12h-9h-6h-3h-24hNOWpk 2413SUSTGUST
−24h−18h−12h−6hnow
A fresh breeze drives the wsw-bound air across the harbor.
Port Costa, CA
Barometer · 24h pressure · mb
STORMRAINCHANGEFAIRDRY9901000101010201030
Pressure · mb
1012.2
+0.7 mb in 3h · rising · 29.89 inHg
Now
1012.2
mb
3h
+0.7
mb
12h
+0.8
mb
24h
-0.2
mb
Regime · CHANGE
STORM
RAIN
CHANGE
FAIR
DRY
24h · Pressure · mb
range 1010–1013
9951000STORM|RAIN10051010RAIN|CHG1015CHG|FAIR10201025FAIR|DRY1030-21h-18h-15h-12h-9h-6h-3h-24hNOW1012.51010.01012.2
−24h−18h−12h−6hnow
Air sits at the threshold — small shifts decide the day.
Port Costa, CA
Air quality
30
AQI
Good
→-3 in 6h

AQI 30 (Good), driven by PM2.5. AQI flat over the last 6 hours (within ±3 points). PM2.5 at 5.1 µg/m³, PM10 at 6.6 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 2.5DRIVERGood
5.1μg/m³
PM 10Good
7μg/m³
NO₂Good
5μg/m³
OzoneGood
47μg/m³
UV IndexModerate
3.6

What's driving it

PM × Wind × Precip

PM2.5 at 5.1 µg/m³, PM10 at 6.6 µg/m³ — typical background levels with no transport signature.

PM2.5/PM10
0.77
Wind
breezy
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/m³300
Port Costa, CA
Sky cover · visibility · 24h
Cloud cover
17%
CLEAR
100%0%−24h−18h−12h−6hnow
Visibility
40.4mi
UNLIMITED
83 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
17:02 UTC · Port Costa, 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
17:02 UTC · Port Costa, CA · NOAA NESDIS / STAR · 5-min cadence · up to 10000 px
Port Costa, CA
Satellite · infrared · animated
Port Costa, CA
Loading IR frames…
IR · cloud-top temp© RainViewer · Carto
Port Costa, CA
Almanac · Sunday, July 5
If the first of July be rainy weather, 'twill rain more or less for four weeks together.
Civil dawn
5:21 AM
Sunrise
10:52 PM
Daylight
14h 42m
Sunset
1:34 PM
Civil dusk
9:07 PM
Planting note
Harvest early potatoes. Begin drying onions on the surface.
Port Costa, CA
The moon
Waning Gibbous
71% illuminated
Moonrise
11:28 PM
Moonset
11:27 AM
In sign
♓︎ Pisces
Port Costa, 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 →

Port Costa at a glance

  • Today vs. normal: 11°F below the seasonal normal for this latitude
  • Last frost: April 4 (climatological average for this latitude)
  • Microseason: Jul 1–5
  • Planting window: Harvest early potatoes. Begin drying onions on the surface.

ZIP code: 94569

16-Day Forecast — Port Costa

  1. Sun70°54°1%
  2. Mon68°54°1%
  3. Tue71°53°3%
  4. Wed76°56°0%
  5. Thu75°58°0%
  6. Fri79°57°0%
  7. Sat82°60°0%
  8. Sun85°60°1%
  9. Mon93°68°3%
  10. Tue88°67°6%
  11. Wed73°63°0%
  12. Thu94°68°3%
  13. Fri101°72°0%
  14. Sat101°76°3%
  15. Sun87°65°0%
  16. Mon76°61°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

September is Port Costa's warmest stretch (~71°F) and January its coldest (~50°F); precipitation crests in December at 4.5 inches and ebbs in July to 0.0 inches.

MonthMean tempPrecipRainy days
January50°4.5″15
February54°3.6″12
March57°3.2″11
April60°1.4″5
May65°0.8″3
June69°0.2″1
July71°0.0″1
August71°0.0″1
September71°0.1″1
October66°1.0″3
November56°2.2″7
December50°4.5″15

Frequently asked

When does it freeze in Port Costa?
In Port Costa, expect the last spring frost near mid-April; Port Costa's first autumn frost comes around mid-November.
What is the rainy season in Port Costa?
December is the wettest month in Port Costa, about 4.5 inches on average; the year totals roughly 21 inches.
What is the warmest month in Port Costa?
Port Costa peaks in September, when the mean runs near 71°F.
What is the coldest month in Port Costa?
January is Port Costa's coldest month, averaging about 50°F.
When can I start a vegetable garden in Port Costa?
In Port Costa, sow peas and hardy greens around mid-April; Port Costa's tomatoes and peppers wait two weeks more.
How many rainy days does Port Costa get?
Expect roughly 75 wet days a year in Port Costa.
What hardiness zone is Port Costa?
Since January in Port Costa averages 50°F, Port Costa's USDA zone follows that floor — confirm it by ZIP.
What is the 10-day forecast for Port Costa?
Port Costa'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 Port Costa?
See this week's day-by-day rain chances for Port Costa in the daily forecast above, and the next 24 hours in the hourly chart.
What is the weather like right now in Port Costa?
Current conditions for Port Costa and the next 24 hours — temperature, precipitation chance, and wind by the hour — are in the hourly forecast chart above.
How often is the Port Costa forecast updated?
The Port Costa forecast on this page is built from Open-Meteo weather-model data and refreshes regularly through the day.
When are sunrise and sunset in Port Costa?
Today's sunrise and sunset times for Port Costa 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 Port Costa?
The next few days in Port Costa's forecast are the most reliable; accuracy declines beyond about a week as weather-model uncertainty grows.

Climate

In Port Costa, California, the hot-summer Mediterranean climate runs from about 50°F in January to 71°F in July, a 21°F seasonal range.

Across the year, Port Costa collects about 21 inches of precipitation over roughly 75 days with measurable rain or snow.

From 38.0°N, Port Costa sees a 21°F seasonal swing that governs Port Costa's planting and frost windows.

All cities in California →

Vallejo, CA weather →

ZIP codes in Port Costa

  • 94569

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.