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September Weather in San Bruno, Mexico

Last updated: August 26, 2025

In September, the average temperature in San Bruno, Mexico hovers around 29°C (85°F). Expect a comfortable minimum of 18°C (65°F), while the mercury can soar to a maximum of 37°C (99°F). Rainfall is moderate, with 39 mm (1.6 in) expected over 3 days, and the average humidity sits at a relatively high 76%.

September Temperature in San Bruno

In September in San Bruno, the average temperature is 29°C (85°F), with maximums reaching 37°C (99°F) and minimums dropping as low as 18°C (65°F). This climate makes it a great time for travelers to enjoy outdoor activities while staying hydrated and seeking shade during the hotter hours.

September Weather in San Bruno: Daily Temperature Highs, Lows, and Averages

The chart illustrates September temperature patterns in San Bruno, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In San Bruno, September typically has an average temperature of 29°C (85°F), with highs reaching up to 37°C (99°F) and lows dropping to around 18°C (65°F).
JanFebMarAprMayJunJulAugSepOctNovDec626266727683878884797163
Data source: Temperature data for San Bruno generated using information from the Copernicus Climate Change Service.
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The average of daily temperatures (24 hours) calculated across all days in the month.

September Precipitation in San Bruno

In San Bruno in September, the total precipitation amount is 39 mm (1.6 in) over a span of 3 days.

September Precipitation Trends in San Bruno

The chart displays monthly precipitation patterns in San Bruno, with values for each month alongside September’s data, which is highlighted for easy comparison. It shows the amount of precipitation, providing insights into how September’s conditions compare to those of other months. In San Bruno, September typically receives around 39 mm (1.6 inches) of precipitation spread over approximately 3 days.
JanFebMarAprMayJunJulAugSepOctNovDec1058001814396109
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in San Bruno

In San Bruno in September, humidity is 76%. With an average temperature of 29°C (85°F), this humidity feels like a warm, heavy blanket enveloping you, making outdoor exploration a sticky challenge but the lush surroundings and vibrant culture offer refreshing experiences in the shade.

September Average Humidity in San Bruno

This chart illustrates the average monthly humidity levels in San Bruno, with September’s data highlighted for easy comparison. It shows the fluctuation in humidity throughout the year, helping you understand how conditions vary by season. In September, average humidity in San Bruno is approximately 76%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec71%66%59%52%51%51%61%73%76%72%72%72%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in San Bruno

In San Bruno in September, the maximum UV index is 12, which corresponds to an extreme Exposure Category. The time to burn is just 10 minutes, underscoring the importance of sun protection. For detailed information, you can check the Hourly UV Index in San Bruno.

Maximum UV Index Levels in San Bruno for September

The chart shows the monthly maximum UV Index (UVI) for San Bruno in September, representing the highest UV radiation level. The UVI measures the intensity of ultraviolet radiation from the sun, indicating the potential risk of sunburn and UV-related health issues. In September, the maximum UV index in San Bruno typically reaches 12, which falls under the extreme exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec6810121212121212975
Data source: San Bruno September UVI data generated using information from the Copernicus Climate Change Service.

UV Risk Categories

  •  Extreme (11+): Avoid the sun, stay in shade.
  •  Very High (8-10): Limit sun exposure.
  •  High (6-7): Use SPF 30+ and protective clothing.
  •  Moderate (3-5): Midday shade recommended.
  •  Low (0-2): No protection needed.

How September Weather in San Bruno Compares to Other Months

Weather in San Bruno varies notably across the year, with each month offering distinct climate conditions. This page compares September’s weather to other months in San Bruno, focusing on differences in temperature, rainfall, humidity, and UV levels.

This table compares monthly weather conditions in San Bruno, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather16°C (62°F)10 mm (0.4 inches)71%high
February Weather17°C (63°F)5 mm (0.2 inches)66%very high
March Weather19°C (66°F)8 mm (0.3 inches)58%very high
April Weather22°C (72°F)0 mm (0.0 inches)52%extreme
May Weather24°C (76°F)0 mm (0.0 inches)51%extreme
June Weather29°C (84°F)1 mm (0.0 inches)51%extreme
July Weather31°C (88°F)8 mm (0.3 inches)60%extreme
August Weather31°C (88°F)14 mm (0.5 inches)73%extreme
September Weather29°C (85°F)39 mm (1.6 inches)76%extreme
October Weather26°C (79°F)6 mm (0.2 inches)72%very high
November Weather22°C (71°F)10 mm (0.4 inches)72%high
December Weather17°C (63°F)9 mm (0.4 inches)72%moderate

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