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September Weather in Walnut, United States

Last updated: June 24, 2025

In September, the average temperature in Walnut, United States hovers around 20°C (69°F), with a range that can drop to a chilly 4°C (40°F) at night and soar to a sizzling 35°C (96°F) during the day. Expect approximately 98 mm (3.8 in) of precipitation spread over 10 days, contributing to an average humidity level of 75%. Whether you're soaking up the sun or dodging the rain, this month promises a variety of weather experiences!

September Temperature in Walnut

In September in Walnut, the average temperature is 20°C (69°F). Maximum temperatures can reach 35°C (96°F), while minimum temperatures can drop as low as 4°C (40°F). Be prepared for a range of weather conditions when traveling during this month in Walnut.

September Weather in Walnut: Daily Temperature Highs, Lows, and Averages

The chart illustrates September temperature patterns in Walnut, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Walnut, September typically has an average temperature of 20°C (69°F), with highs reaching up to 35°C (96°F) and lows dropping to around 4°C (40°F).
JanFebMarAprMayJunJulAugSepOctNovDec232440496274777368523930
Data source: Temperature data for Walnut 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 Walnut

In Walnut in September, the precipitation amount is 98 mm (3.8 in) spread over a period of 10 days.

September Precipitation Trends in Walnut

The chart displays monthly precipitation patterns in Walnut, 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 Walnut, September typically receives around 98 mm (3.8 inches) of precipitation spread over approximately 10 days.
JanFebMarAprMayJunJulAugSepOctNovDec3036865715710968108981283436
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in Walnut

In Walnut in September, humidity is 75%. With an average temperature of 20°C (69°F), this humidity feels like a warm, enveloping blanket, making travel a bit muggy and requiring frequent hydration breaks to stay comfortable while exploring.

September Average Humidity in Walnut

This chart illustrates the average monthly humidity levels in Walnut, 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 Walnut is approximately 75%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec76%80%73%75%78%82%83%81%75%75%82%83%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Walnut

In Walnut in September, the maximum UV index is 8, which corresponds to a very high Exposure Category. This means that the time to burn is only 15 minutes. For more detailed information, you can refer to the Hourly UV Index in Walnut.

Maximum UV Index Levels in Walnut for September

The chart shows the monthly maximum UV Index (UVI) for Walnut 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 Walnut typically reaches 8, which falls under the very high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec356810111098643
Data source: Walnut 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 Walnut Compares to Other Months

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

This table compares monthly weather conditions in Walnut, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather-5°C (24°F)30 mm (1.2 inches)76%moderate
February Weather-4°C (24°F)36 mm (1.4 inches)80%moderate
March Weather4°C (40°F)86 mm (3.4 inches)73%high
April Weather9°C (49°F)57 mm (2.3 inches)74%very high
May Weather17°C (62°F)157 mm (6.2 inches)78%very high
June Weather24°C (75°F)109 mm (4.3 inches)82%extreme
July Weather25°C (77°F)68 mm (2.7 inches)83%very high
August Weather23°C (74°F)108 mm (4.3 inches)80%very high
September Weather20°C (69°F)98 mm (3.8 inches)75%very high
October Weather11°C (52°F)128 mm (5.0 inches)75%high
November Weather4°C (39°F)34 mm (1.3 inches)82%moderate
December Weather-1°C (31°F)36 mm (1.4 inches)83%moderate

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