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United States weather

Weather in San Mateo, California for September 2026

Your guide to San Mateo weather in September - trends and predictions

    Temperatures

  • So far, September 2026 in San Mateo shows a warmer trend than usual by 4.3 °F.

  • The forecast for the next days in San Mateo predicts temperatures to be around 22 °F, close to the historical average.

  • In general, the average temperature in San Mateo at the beginning of September is 21.7 °F. As the month progressed, temperatures tended to moderately fall, reaching an average of 20.9 °F by the end of September.

    • Rain 🌧️

  • Precipitation in San Mateo during September is a rare event, with an average of fewer than 2 rainy days.

    • More

  • New! Chat with our AI weatherman - it’s amazing and free.

Average dry days
29
Dry days
Average rainy days
1
Rainy days
Average snowy days
0
Snow days
Average temperatures
20°/14°
Temperatures
Average wind speed
16 km/h
Avg max wind
Average humidity
81 %
Avg humidity

San Mateo Weather September

Move between months or click on a day
August
October
Sun.Mon.Tue.Wed.Thu.Fri.Sat.
1
Cloudy
20°
2
Sunny
20°
3
Sunny
22°
4
Sunny
23°
5
Sunny
22°
6
Overcast
21°
7
Cloudy
24°
8
Cloudy
24°
9
Overcast
23°
10
Overcast
21°
11
Sunny
19°
12
Sunny
20°
13
Sunny
20°
14
Sunny
24°
15
Sunny
23°
16
Sunny
23°
17
Sunny
23°
18
Sunny
22°
19
Partly cloudy
22°
20
Overcast
22°
21
Overcast
21°
22
Sunny
24°
23
Sunny
24°
24
Overcast
20°
25
Sunny
21°
26
Sunny
22°
27
Overcast
22°
28
Overcast
18°
29
Overcast
19°
30
Partly cloudy
24°

Temperatures trend during September in San Mateo

See the weather trend as well as the moving average line

September weather in San Mateo day by day

Click on a date for more information
August October
Date Weather Temperatures Rain UV More
Sept. 1 Cloudy
Cloudy
 20° /13° 0.9 mm 4
Sept. 2 Sunny
Sunny
 20° /13° 0 mm 6
Sept. 3 Sunny
Sunny
 22° /13° 0.2 mm 5
Sept. 4 Sunny
Sunny
 23° /13° 0 mm 6
Sept. 5 Sunny
Sunny
 22° /13° 0 mm 6
Sept. 6 Overcast
Overcast
 21° /12° 0 mm 6
Sept. 7 Cloudy
Cloudy
 24° /12° 0 mm 6
Sept. 8 Cloudy
Cloudy
 24° /12° 0 mm 5
Sept. 9 Overcast
Overcast
 23° /15° 0 mm 3
Sept. 10 Overcast
Overcast
 21° /14° 0 mm 5
Sept. 11 Sunny
Sunny
 19° /13° 0 mm 6
Sept. 12 Sunny
Sunny
 20° /13° 0 mm 6
Sept. 13 Sunny
Sunny
 20° /13° 0 mm 7.3
Sept. 14 Sunny
Sunny
 24° /12° 0 mm 6.5
Sept. 15 Sunny
Sunny
 23° /12° 0 mm 6.6
Sept. 16 Sunny
Sunny
 23° /12° 0 mm 6.7
Sept. 17 Sunny
Sunny
 23° /13° 0 mm 6
Sept. 18 Sunny
Sunny
 22° /13° 0 mm 6
Sept. 19 Partly cloudy
Partly cloudy
 22° /13° 0 mm 6
Sept. 20 Overcast
Overcast
 22° /13° 0 mm 5
Sept. 21 Overcast
Overcast
 21° /13° 0 mm 6
Sept. 22 Sunny
Sunny
 24° /13° 0 mm 6
Sept. 23 Sunny
Sunny
 24° /13° 0 mm 6
Sept. 24 Overcast
Overcast
 20° /13° 0 mm 5
Sept. 25 Sunny
Sunny
 21° /12° 0 mm 6
Sept. 26 Sunny
Sunny
 22° /12° 0 mm 6
Sept. 27 Overcast
Overcast
 22° /13° 0 mm 5
Sept. 28 Overcast
Overcast
 18° /14° 0 mm 4
Sept. 29 Overcast
Overcast
 19° /13° 0 mm 5
Sept. 30 Partly cloudy
Partly cloudy
 24° /14° 0 mm 6
Next
Important Notice
Our weather forecast for San Mateo in September is based on the analysis of historical data rather than real-time forecast models. While this provides a general overview, weather conditions can change. We recommend that you check the San Mateo forecast closer to your planned date for the most up-to-date weather information.
Change Month
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San Mateo in September - FAQ

What are the expected maximum and minimum temperatures in San Mateo during September?
Enjoy moderate daytime temperatures of up to 20° and cooler nights around 14°. Ideal for a range of outdoor activities, from hiking to city tours.

How much rainfall should be expected in San Mateo during September?
Expect minimal rainfall in San Mateo during September, with a total of 18.2 mm over approximately 1 days. This minimal precipitation is unlikely to significantly impact plans.

What are the typical wind conditions in San Mateo during September?
The average wind speed in San Mateo during September is 16 km/h, suggesting breezy to windy conditions, depending on your activities.

UV exposure in San Mateo during September

Stay informed about UV levels for safe outdoor activities throughout the month of September ☀️

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Location coordinates Where is San Mateo?

Get accurate weather forecasts for San Mateo, located at latitude 37.563 and longitude -122.326. Stay updated with localized weather information tailored for San Mateo.

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