Hourly Weather Forecast for San Mateo, California

Hourly Weather | Today › Sunday, October 4, 2026

Active Weather Warnings

Heat Advisory

San Mateo, California

2 AM

70°

Feels Like 66°

Humidity: 59%

UV Index: 0

Wind: 5 mph

3 AM

68°

Feels Like 64°

Humidity: 65%

UV Index: 0

Wind: 5 mph

4 AM

66°

Feels Like 64°

Humidity: 67%

UV Index: 0

Wind: 4 mph

5 AM

66°

Feels Like 64°

Humidity: 68%

UV Index: 0

Wind: 4 mph

6 AM

64°

Feels Like 63°

Humidity: 70%

UV Index: 0

Wind: 4 mph

7 AM

64°

Feels Like 64°

Humidity: 72%

UV Index: 0

Wind: 4 mph

8 AM

66°

Feels Like 66°

Humidity: 66%

UV Index: 1

Wind: 4 mph

9 AM

72°

Feels Like 73°

Humidity: 59%

UV Index: 2

Wind: 4 mph

10 AM

75°

Feels Like 79°

Humidity: 52%

UV Index: 3

Wind: 4 mph

11 AM

81°

Feels Like 84°

Humidity: 47%

UV Index: 4

Wind: 5 mph

12 PM

84°

Feels Like 88°

Humidity: 42%

UV Index: 4

Wind: 6 mph

1 PM

88°

Feels Like 90°

Humidity: 38%

UV Index: 5

Wind: 7 mph

2 PM

90°

Feels Like 91°

Humidity: 36%

UV Index: 4

Wind: 8 mph

3 PM

90°

Feels Like 91°

Humidity: 35%

UV Index: 3

Wind: 8 mph

4 PM

88°

Feels Like 88°

Humidity: 37%

UV Index: 2

Wind: 9 mph

5 PM

84°

Feels Like 84°

Humidity: 41%

UV Index: 2

Wind: 9 mph

6 PM

82°

Feels Like 81°

Humidity: 44%

UV Index: 1

Wind: 8 mph

7 PM

79°

Feels Like 77°

Humidity: 47%

UV Index: 0

Wind: 7 mph

8 PM

75°

Feels Like 73°

Humidity: 53%

UV Index: 0

Wind: 6 mph

9 PM

73°

Feels Like 72°

Humidity: 58%

UV Index: 0

Wind: 6 mph

10 PM

70°

Feels Like 68°

Humidity: 64%

UV Index: 0

Wind: 6 mph

11 PM

72°

Feels Like 70°

Humidity: 63%

UV Index: 0

Wind: 6 mph

Hourly Air Quality Forecast - AQI (US EPA)

2 AM

30 AQI

Good air quality Dominant pollutant: PM_2.5

Details

Pollutant Concentrations:

PM_2.5: 7.17 µg/m³
PM₁₀: 14.28 µg/m³
O₃: 0.033 ppm
NO₂: 1.1 ppb
SO₂: 0.3 ppb
CO: 0.10 ppm

Health Recommendations:

Air quality is considered satisfactory, and air pollution poses little or no risk.

3 AM

30 AQI

Good air quality Dominant pollutant: O₃

Details

Pollutant Concentrations:

PM_2.5: 6.73 µg/m³
PM₁₀: 13.44 µg/m³
O₃: 0.032 ppm
NO₂: 1.1 ppb
SO₂: 0.3 ppb
CO: 0.10 ppm

Health Recommendations:

Air quality is considered satisfactory, and air pollution poses little or no risk.

4 AM

29 AQI

Good air quality Dominant pollutant: O₃

Details

Pollutant Concentrations:

PM_2.5: 6.35 µg/m³
PM₁₀: 12.76 µg/m³
O₃: 0.031 ppm
NO₂: 1.2 ppb
SO₂: 0.3 ppb
CO: 0.10 ppm

Health Recommendations:

Air quality is considered satisfactory, and air pollution poses little or no risk.

5 AM

28 AQI

Good air quality Dominant pollutant: O₃

Details

Pollutant Concentrations:

PM_2.5: 6.08 µg/m³
PM₁₀: 12.25 µg/m³
O₃: 0.031 ppm
NO₂: 1.2 ppb
SO₂: 0.3 ppb
CO: 0.10 ppm

Health Recommendations:

Air quality is considered satisfactory, and air pollution poses little or no risk.

6 AM

28 AQI

Good air quality Dominant pollutant: O₃

Details

Pollutant Concentrations:

PM_2.5: 5.87 µg/m³
PM₁₀: 11.86 µg/m³
O₃: 0.030 ppm
NO₂: 1.2 ppb
SO₂: 0.3 ppb
CO: 0.10 ppm

Health Recommendations:

Air quality is considered satisfactory, and air pollution poses little or no risk.

7 AM

28 AQI

Good air quality Dominant pollutant: O₃

Details

Pollutant Concentrations:

PM_2.5: 5.73 µg/m³
PM₁₀: 11.68 µg/m³
O₃: 0.030 ppm
NO₂: 1.2 ppb
SO₂: 0.3 ppb
CO: 0.10 ppm

Health Recommendations:

Air quality is considered satisfactory, and air pollution poses little or no risk.

8 AM

28 AQI

Good air quality Dominant pollutant: O₃

Details

Pollutant Concentrations:

PM_2.5: 5.65 µg/m³
PM₁₀: 11.65 µg/m³
O₃: 0.030 ppm
NO₂: 1.3 ppb
SO₂: 0.3 ppb
CO: 0.10 ppm

Health Recommendations:

Air quality is considered satisfactory, and air pollution poses little or no risk.

9 AM

27 AQI

Good air quality Dominant pollutant: O₃

Details

Pollutant Concentrations:

PM_2.5: 5.66 µg/m³
PM₁₀: 11.72 µg/m³
O₃: 0.029 ppm
NO₂: 1.3 ppb
SO₂: 0.3 ppb
CO: 0.10 ppm

Health Recommendations:

Air quality is considered satisfactory, and air pollution poses little or no risk.

10 AM

27 AQI

Good air quality Dominant pollutant: O₃

Details

Pollutant Concentrations:

PM_2.5: 5.75 µg/m³
PM₁₀: 11.98 µg/m³
O₃: 0.029 ppm
NO₂: 1.2 ppb
SO₂: 0.3 ppb
CO: 0.10 ppm

Health Recommendations:

Air quality is considered satisfactory, and air pollution poses little or no risk.

11 AM

28 AQI

Good air quality Dominant pollutant: O₃

Details

Pollutant Concentrations:

PM_2.5: 6 µg/m³
PM₁₀: 12.6 µg/m³
O₃: 0.030 ppm
NO₂: 1.1 ppb
SO₂: 0.3 ppb
CO: 0.10 ppm

Health Recommendations:

Air quality is considered satisfactory, and air pollution poses little or no risk.

12 PM

29 AQI

Good air quality Dominant pollutant: O₃

Details

Pollutant Concentrations:

PM_2.5: 6.47 µg/m³
PM₁₀: 13.71 µg/m³
O₃: 0.031 ppm
NO₂: 0.8 ppb
SO₂: 0.3 ppb
CO: 0.10 ppm

Health Recommendations:

Air quality is considered satisfactory, and air pollution poses little or no risk.

1 PM

32 AQI

Good air quality Dominant pollutant: O₃

Details

Pollutant Concentrations:

PM_2.5: 7.13 µg/m³
PM₁₀: 15.29 µg/m³
O₃: 0.034 ppm
NO₂: 0.6 ppb
SO₂: 0.3 ppb
CO: 0.10 ppm

Health Recommendations:

Air quality is considered satisfactory, and air pollution poses little or no risk.

2 PM

34 AQI

Good air quality Dominant pollutant: O₃

Details

Pollutant Concentrations:

PM_2.5: 7.82 µg/m³
PM₁₀: 16.88 µg/m³
O₃: 0.037 ppm
NO₂: 0.5 ppb
SO₂: 0.3 ppb
CO: 0.10 ppm

Health Recommendations:

Air quality is considered satisfactory, and air pollution poses little or no risk.

3 PM

37 AQI

Good air quality Dominant pollutant: O₃

Details

Pollutant Concentrations:

PM_2.5: 8.27 µg/m³
PM₁₀: 17.65 µg/m³
O₃: 0.040 ppm
NO₂: 0.4 ppb
SO₂: 0.3 ppb
CO: 0.10 ppm

Health Recommendations:

Air quality is considered satisfactory, and air pollution poses little or no risk.

4 PM

39 AQI

Good air quality Dominant pollutant: O₃

Details

Pollutant Concentrations:

PM_2.5: 8.45 µg/m³
PM₁₀: 17.82 µg/m³
O₃: 0.042 ppm
NO₂: 0.4 ppb
SO₂: 0.3 ppb
CO: 0.10 ppm

Health Recommendations:

Air quality is considered satisfactory, and air pollution poses little or no risk.

5 PM

40 AQI

Good air quality Dominant pollutant: O₃

Details

Pollutant Concentrations:

PM_2.5: 8.45 µg/m³
PM₁₀: 17.73 µg/m³
O₃: 0.044 ppm
NO₂: 0.4 ppb
SO₂: 0.3 ppb
CO: 0.10 ppm

Health Recommendations:

Air quality is considered satisfactory, and air pollution poses little or no risk.

6 PM

41 AQI

Good air quality Dominant pollutant: O₃

Details

Pollutant Concentrations:

PM_2.5: 8.34 µg/m³
PM₁₀: 17.38 µg/m³
O₃: 0.044 ppm
NO₂: 0.5 ppb
SO₂: 0.3 ppb
CO: 0.10 ppm

Health Recommendations:

Air quality is considered satisfactory, and air pollution poses little or no risk.

7 PM

40 AQI

Good air quality Dominant pollutant: O₃

Details

Pollutant Concentrations:

PM_2.5: 8.23 µg/m³
PM₁₀: 16.9 µg/m³
O₃: 0.043 ppm
NO₂: 0.7 ppb
SO₂: 0.3 ppb
CO: 0.10 ppm

Health Recommendations:

Air quality is considered satisfactory, and air pollution poses little or no risk.

8 PM

39 AQI

Good air quality Dominant pollutant: O₃

Details

Pollutant Concentrations:

PM_2.5: 8.25 µg/m³
PM₁₀: 16.63 µg/m³
O₃: 0.042 ppm
NO₂: 0.7 ppb
SO₂: 0.3 ppb
CO: 0.10 ppm

Health Recommendations:

Air quality is considered satisfactory, and air pollution poses little or no risk.

9 PM

38 AQI

Good air quality Dominant pollutant: O₃

Details

Pollutant Concentrations:

PM_2.5: 8.45 µg/m³
PM₁₀: 16.72 µg/m³
O₃: 0.041 ppm
NO₂: 0.7 ppb
SO₂: 0.3 ppb
CO: 0.10 ppm

Health Recommendations:

Air quality is considered satisfactory, and air pollution poses little or no risk.

10 PM

37 AQI

Good air quality Dominant pollutant: PM_2.5

Details

Pollutant Concentrations:

PM_2.5: 8.82 µg/m³
PM₁₀: 17.17 µg/m³
O₃: 0.040 ppm
NO₂: 0.8 ppb
SO₂: 0.3 ppb
CO: 0.11 ppm

Health Recommendations:

Air quality is considered satisfactory, and air pollution poses little or no risk.

11 PM

39 AQI

Good air quality Dominant pollutant: PM_2.5

Details

Pollutant Concentrations:

PM_2.5: 9.28 µg/m³
PM₁₀: 17.83 µg/m³
O₃: 0.039 ppm
NO₂: 0.9 ppb
SO₂: 0.3 ppb
CO: 0.11 ppm

Health Recommendations:

Air quality is considered satisfactory, and air pollution poses little or no risk.

Current Real-Time Air Quality Report

Weather Alerts and Warnings for San Mateo

Moderate Expected Likely

Heat Advisory

Heat Advisory issued October 3 at 7:48PM PDT until October 7 at 10:00PM PDT by NWS San Francisco CA

Oct 3, 7:48 PM → Oct 7, 10:00 PM

WHAT: Hot conditions with maximum temperatures in the mid-90s to
low-100s. Mild minimum temperatures and weak onshore flow will
limit overnight relief.

WHERE: The East Bay and San Francisco Bay Shoreline, North Bay
Interior Mountains and Valleys, The Santa Clara Valley and Eastern
Hills, The Santa Cruz Mountains, Interior Monterey County and the
Santa Lucia Range, Most of San Benito County and the Cholame Hills
in Southeast Monterey County, and Southern Salinas Valley/Arroyo
Seco and Lake San Antonio.

WHEN: Until 10 PM PDT Wednesday.

IMPACTS: This level of heat affects anyone without effective
cooling and/or adequate hydration. Impacts likely in some health
systems, heat-sensitive industries and infrastructure.

+ Read More

Hydration is a critical piece to surviving the heat. Drink water, and if possible, take water to those who are vulnerable. Take extra precautions when outside. Wear lightweight and loose fitting clothing. Try to limit strenuous activities to the early morning or evening. Take action when you experience symptoms of heat exhaustion and/or heat stroke. Beat the heat and check the backseat! Do not leave young children or pets in unattended vehicles. Car interiors will reach lethal temperatures in a matter of minutes.

Updated: Oct 4, 1:25 AM Source: NWS Alert

Hourly Air Quality Forecast - AQI (US EPA)

Pollutant Concentrations:

Health Recommendations:

Pollutant Concentrations:

Health Recommendations:

Pollutant Concentrations:

Health Recommendations:

Pollutant Concentrations:

Health Recommendations:

Pollutant Concentrations:

Health Recommendations:

Pollutant Concentrations:

Health Recommendations:

Pollutant Concentrations:

Health Recommendations:

Pollutant Concentrations:

Health Recommendations:

Pollutant Concentrations:

Health Recommendations:

Pollutant Concentrations:

Health Recommendations:

Pollutant Concentrations:

Health Recommendations:

Pollutant Concentrations:

Health Recommendations:

Pollutant Concentrations:

Health Recommendations:

Pollutant Concentrations:

Health Recommendations:

Pollutant Concentrations:

Health Recommendations:

Pollutant Concentrations:

Health Recommendations:

Pollutant Concentrations:

Health Recommendations:

Pollutant Concentrations:

Health Recommendations:

Pollutant Concentrations:

Health Recommendations:

Pollutant Concentrations:

Health Recommendations:

Pollutant Concentrations:

Health Recommendations:

Pollutant Concentrations:

Health Recommendations:

Weather Alerts and Warnings for San Mateo

Heat Advisory

Explore U.S. Weather Trends