As of 03:11 PDT

Weather in Port Costa, CA

60°

Port Costa, Sunday, 9 August, 03:11

Clear. Feels like 59°. High 90°, low 60°.

Pressure29.83 inHg

Wind8 mph SW

Humidity83%

Visibility6.2 mi

Dew point55°

See detailed hourly forecast

Monthly outlook for Port Costa, CA: average high 76.7°, average low 60.7°. That is 3° below the climate normal for August. Precipitation is expected on 0 days (about 0.0 inches), against a normal of 0 days and 0.0 inches. The warmest day looks like 9 August (89.6°), the coolest 24 August (58.6°).

76.7°/60.7°

Average high / low

−3°

Below normal

0 / 0

Wet days / normal

0.0 in

Precipitation this month

Ten-day blocks vs climate normal

Period	Forecast high	Normal	Difference
9 August – 18 August	77.7°	82.7°	-2.8°
19 August – 28 August	75°	82°	-3.9°
29 August – 7 September	at normal	83.8°	—

August records over 66 years

104.2°4 August 1998All-time high

49.1°10 August 1960All-time low

Climate normals and records are computed from the nearest reference point — Vallejo (5 mi).

Mon, 1086° / 60°

86 °

Port Costa, Monday, 10 August

Clear. High 86°, low 60°.

Pressure29.85 inHg

Wind8.6 mph SW

Humidity43%

Visibility6.2 mi

Dew point51°

Tue, 1177° / 60°

77 °

Port Costa, Tuesday, 11 August

Clear. High 77°, low 60°.

Pressure29.91 inHg

Wind8.1 mph SW

Humidity42%

Visibility6.2 mi

Dew point51°

Wed, 1274° / 60°

74 °

Port Costa, Wednesday, 12 August

Clear. High 74°, low 60°.

Pressure29.85 inHg

Wind9.8 mph SW

Humidity50%

Visibility6.2 mi

Dew point53°

Thu, 1373° / 61°

73 °

Port Costa, Thursday, 13 August

Mostly clear. High 73°, low 61°.

Pressure29.85 inHg

Wind14.5 mph SW

Humidity53%

Visibility—

Dew point53°

Fri, 1475° / 61°

75 °

Port Costa, Friday, 14 August

Clear. High 75°, low 61°.

Pressure29.94 inHg

Wind13.6 mph SW

Humidity46%

Visibility—

Dew point51°

Sat, 1577° / 60°

77 °

Port Costa, Saturday, 15 August

Mostly clear. High 77°, low 60°.

Pressure30.00 inHg

Wind13.5 mph SW

Humidity43%

Visibility—

Dew point51°

Sun, 1676° / 63°

76 °

Port Costa, Sunday, 16 August

Overcast. High 76°, low 63°.

Pressure30.06 inHg

Wind14.3 mph SW

Humidity45%

Visibility—

Dew point52°

Mon, 1773° / 60°

73 °

Port Costa, Monday, 17 August

Overcast. High 73°, low 60°.

Pressure30.09 inHg

Wind11.6 mph SW

Humidity47%

Visibility—

Dew point51°

Tue, 1877° / 61°

77 °

Port Costa, Tuesday, 18 August

Overcast. High 77°, low 61°.

Pressure30.00 inHg

Wind12.3 mph SW

Humidity52%

Visibility—

Dew point56°

Wed, 1979° / 64°

79 °

Port Costa, Wednesday, 19 August

Clear. High 79°, low 64°.

Pressure29.94 inHg

Wind12.3 mph SW

Humidity51%

Visibility—

Dew point57°

Thu, 2079° / 63°

79 °

Port Costa, Thursday, 20 August

Overcast. High 79°, low 63°.

Pressure29.94 inHg

Wind11.9 mph SW

Humidity48%

Visibility—

Dew point55°

Fri, 2172° / 60°

72 °

Port Costa, Friday, 21 August

Overcast. High 72°, low 60°.

Pressure29.94 inHg

Wind13.7 mph SW

Humidity48%

Visibility—

Dew point50°

Sat, 2273° / 60°

73 °

Port Costa, Saturday, 22 August

Overcast. High 73°, low 60°.

Pressure29.94 inHg

Wind11.1 mph SW

Humidity47%

Visibility—

Dew point50°

Sun, 2373° / 60°

73 °

Port Costa, Sunday, 23 August

Overcast. High 73°, low 60°.

Pressure29.91 inHg

Wind13.6 mph SW

Humidity49%

Visibility—

Dew point51°

Mon, 2474° / 59°

74 °

Port Costa, Monday, 24 August

Clear. High 74°, low 59°.

Pressure29.85 inHg

Wind14.2 mph SW

Humidity46%

Visibility—

Dew point50°

From day 17 onward the outlook is built from 60-year climate statistics

Tue, 2582° / 57°

82 °

Port Costa, Tuesday, 25 August

Climate normal for this date — 60-year average.

Average high82°

Average low57°

Average precipitation0 in

Chance of precipitation0%

Record high100° (1988)

Record low52° (1960)

Wed, 2683° / 56°

83 °

Port Costa, Wednesday, 26 August

Climate normal for this date — 60-year average.

Average high83°

Average low56°

Average precipitation0 in

Chance of precipitation0%

Record high100° (1988)

Record low51° (2005)

Thu, 2784° / 57°

84 °

Port Costa, Thursday, 27 August

Climate normal for this date — 60-year average.

Average high84°

Average low57°

Average precipitation0 in

Chance of precipitation0%

Record high99° (2008)

Record low52° (1960)

Fri, 2884° / 57°

84 °

Port Costa, Friday, 28 August

Climate normal for this date — 60-year average.

Average high84°

Average low57°

Average precipitation0 in

Chance of precipitation0%

Record high102° (2008)

Record low51° (1960)

Sat, 2983° / 57°

83 °

Port Costa, Saturday, 29 August

Climate normal for this date — 60-year average.

Average high83°

Average low57°

Average precipitation0 in

Chance of precipitation0%

Record high100° (1977)

Record low51° (1975)

Sun, 3083° / 57°

83 °

Port Costa, Sunday, 30 August

Climate normal for this date — 60-year average.

Average high83°

Average low57°

Average precipitation0 in

Chance of precipitation3%

Record high98° (1996)

Record low52° (1960)

Mon, 3183° / 57°

83 °

Port Costa, Monday, 31 August

Climate normal for this date — 60-year average.

Average high83°

Average low57°

Average precipitation0 in

Chance of precipitation3%

Record high95° (1976)

Record low51° (1970)

Tue, 0185° / 57°

85 °

Port Costa, Tuesday, 1 September

Climate normal for this date — 60-year average.

Average high85°

Average low57°

Average precipitation0 in

Chance of precipitation2%

Record high102° (2017)

Record low51° (1970)

Wed, 0284° / 57°

84 °

Port Costa, Wednesday, 2 September

Climate normal for this date — 60-year average.

Average high84°

Average low57°

Average precipitation0 in

Chance of precipitation2%

Record high102° (2017)

Record low52° (1960)

Thu, 0383° / 57°

83 °

Port Costa, Thursday, 3 September

Climate normal for this date — 60-year average.

Average high83°

Average low57°

Average precipitation0 in

Chance of precipitation0%

Record high98° (1963)

Record low49° (2000)

Fri, 0484° / 57°

84 °

Port Costa, Friday, 4 September

Climate normal for this date — 60-year average.

Average high84°

Average low57°

Average precipitation0 in

Chance of precipitation0%

Record high98° (2008)

Record low50° (2000)

Sat, 0585° / 57°

85 °

Port Costa, Saturday, 5 September

Climate normal for this date — 60-year average.

Average high85°

Average low57°

Average precipitation0 in

Chance of precipitation0%

Record high106° (2022)

Record low51° (2012)

Sun, 0684° / 57°

84 °

Port Costa, Sunday, 6 September

Climate normal for this date — 60-year average.

Average high84°

Average low57°

Average precipitation0 in

Chance of precipitation2%

Record high107° (2022)

Record low51° (1973)

Mon, 0785° / 57°

85 °

Port Costa, Monday, 7 September

Climate normal for this date — 60-year average.

Average high85°

Average low57°

Average precipitation0 in

Chance of precipitation0%

Record high105° (2020)

Record low52° (1960)

About the monthly outlook

How accurate is a 30-day forecast?

The first 16 days come from weather models — reliable for the first 3–5 days and progressively less so after that. Days 17 through 30 for Port Costa, CA are built from the climate normal, the 60-year average, so they show typical weather for those dates rather than a specific forecast.

What does "above normal" mean?

We compare the forecast against the climate normal for those exact calendar days, computed from 60 years of observations. The deviation shows how much the coming month differs from a typical one.

Where do the 66-year records come from?

They are real temperature extremes recorded in Port Costa, CA since 1960: the highest and lowest reading for each calendar date, with the year it happened.

How often is it updated?

The forecast portion refreshes every hour; the climate portion is based on long-term data and stays stable.