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September Weather in Arcata, United States

Last updated: June 24, 2025

In September, the average temperature in Arcata, United States hovers around 15°C (59°F), offering a pleasant climate for outdoor activities. Temperatures can vary, dipping to a minimum of 6°C (43°F) and peaking at a warm 31°C (88°F). Expect some rain with an average precipitation of 29 mm (1.1 in) spread over 3 days, while the air maintains a comfortable humidity level of 62%.

September Temperature in Arcata

In September in Arcata, the average temperature is 15°C (59°F), with maximums reaching up to 31°C (88°F) and minimums dipping as low as 6°C (43°F). Travelers should be prepared for a range of temperatures and pack accordingly to fully enjoy their time in Arcata.

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

The chart illustrates September temperature patterns in Arcata, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Arcata, September typically has an average temperature of 15°C (59°F), with highs reaching up to 31°C (88°F) and lows dropping to around 6°C (43°F).
JanFebMarAprMayJunJulAugSepOctNovDec464546495256596159544945
Data source: Temperature data for Arcata 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 Arcata

In Arcata in September, the precipitation amount is 29 mm (1.1 in) over the course of 3 days.

September Precipitation Trends in Arcata

The chart displays monthly precipitation patterns in Arcata, 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 Arcata, September typically receives around 29 mm (1.1 inches) of precipitation spread over approximately 3 days.
JanFebMarAprMayJunJulAugSepOctNovDec2192121761086422652962133165
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in Arcata

In Arcata in September humidity is 62%. With an average temperature of 15°C (59°F), this humidity feels like a refreshing embrace, making it ideal for leisurely strolls and explorations without feeling overly hot or sticky.

September Average Humidity in Arcata

This chart illustrates the average monthly humidity levels in Arcata, 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 Arcata is approximately 62%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec86%85%85%82%81%79%70%60%62%72%87%86%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Arcata

In Arcata 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 Arcata.

Maximum UV Index Levels in Arcata for September

The chart shows the monthly maximum UV Index (UVI) for Arcata 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 Arcata typically reaches 8, which falls under the very high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec3478101110108642
Data source: Arcata 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 Arcata Compares to Other Months

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

This table compares monthly weather conditions in Arcata, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather8°C (46°F)219 mm (8.6 inches)86%moderate
February Weather7°C (45°F)212 mm (8.3 inches)85%moderate
March Weather8°C (46°F)176 mm (6.9 inches)85%high
April Weather9°C (49°F)108 mm (4.2 inches)82%very high
May Weather11°C (52°F)64 mm (2.5 inches)81%very high
June Weather14°C (57°F)22 mm (0.9 inches)79%extreme
July Weather15°C (59°F)6 mm (0.2 inches)70%very high
August Weather16°C (61°F)5 mm (0.2 inches)60%very high
September Weather15°C (59°F)29 mm (1.1 inches)62%very high
October Weather12°C (54°F)62 mm (2.4 inches)72%high
November Weather10°C (49°F)133 mm (5.2 inches)87%moderate
December Weather7°C (45°F)165 mm (6.5 inches)86%low

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