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September Weather in Mattawa, United States

Last updated: June 24, 2025

In September, the average temperature in Mattawa, United States is 19°C (66°F). Expect a range that can dip as low as 3°C (38°F) and soar to a maximum of 38°C (101°F). During this period, precipitation totals around 14 mm (0.5 in), typically spread over 3 days, and the average humidity sits at 62%.

September Temperature in Mattawa

In September in Mattawa, the average temperature is 19°C (66°F). Maximum temperatures can reach 38°C (101°F) and minimums can be as low as 3°C (38°F). This diverse temperature range makes Mattawa an ideal destination for travelers seeking both warm days and cooler evenings.

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

The chart illustrates September temperature patterns in Mattawa, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Mattawa, September typically has an average temperature of 19°C (66°F), with highs reaching up to 38°C (101°F) and lows dropping to around 3°C (38°F).
JanFebMarAprMayJunJulAugSepOctNovDec313243526370777766514033
Data source: Temperature data for Mattawa 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 Mattawa

In Mattawa in September, the precipitation amount is 14 mm (0.5 in) over the course of 3 days.

September Precipitation Trends in Mattawa

The chart displays monthly precipitation patterns in Mattawa, 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 Mattawa, September typically receives around 14 mm (0.5 inches) of precipitation spread over approximately 3 days.
JanFebMarAprMayJunJulAugSepOctNovDec454328261771514333538
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in Mattawa

In Mattawa in September, humidity is 62%. With an average temperature of 19°C (66°F), this humidity feels like a balmy embrace, making travel pleasant, yet slightly muggy, urging you to stay hydrated and seek shade during midday excursions.

September Average Humidity in Mattawa

This chart illustrates the average monthly humidity levels in Mattawa, 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 Mattawa is approximately 62%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec86%86%87%84%81%82%79%63%62%83%89%88%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Mattawa

In Mattawa in September, the maximum UV index is 7, which corresponds to the high Exposure Category. This means that the time to burn is approximately 25 minutes. For more detailed information, you can check the Hourly UV Index in Mattawa.

Maximum UV Index Levels in Mattawa for September

The chart shows the monthly maximum UV Index (UVI) for Mattawa 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 Mattawa typically reaches 7, which falls under the high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec2356891097532
Data source: Mattawa 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 Mattawa Compares to Other Months

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

This table compares monthly weather conditions in Mattawa, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather-1°C (31°F)45 mm (1.8 inches)86%low
February Weather0°C (33°F)43 mm (1.7 inches)86%moderate
March Weather6°C (43°F)27 mm (1.1 inches)87%moderate
April Weather11°C (52°F)26 mm (1.0 inches)84%high
May Weather17°C (63°F)17 mm (0.7 inches)81%very high
June Weather21°C (70°F)7 mm (0.3 inches)82%very high
July Weather25°C (77°F)1 mm (0.0 inches)79%very high
August Weather25°C (77°F)5 mm (0.2 inches)63%very high
September Weather19°C (66°F)14 mm (0.5 inches)62%high
October Weather11°C (51°F)33 mm (1.3 inches)83%moderate
November Weather4°C (40°F)35 mm (1.4 inches)89%moderate
December Weather0°C (33°F)38 mm (1.5 inches)88%low

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