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September Weather in Mattoon, United States

Last updated: June 24, 2025

In Mattoon, United States, the average temperature in September hovers around 21°C (71°F). Expect a minimum of 6°C (43°F) and a maximum of 33°C (92°F), making for quite a range! Moisture is in the air with an average humidity of 79%, accompanied by 67 mm (2.6 in) of precipitation over 6 days. Whether you're soaking in the warmth or bracing for a sudden shower, it's a month full of vibrant weather!

September Temperature in Mattoon

In September in Mattoon, the average temperature is 21°C (71°F), with maximums reaching 33°C (92°F) and minimums dropping to as low as 6°C (43°F), making it an ideal time for travelers to experience a pleasant climate and enjoy outdoor activities.

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

The chart illustrates September temperature patterns in Mattoon, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Mattoon, September typically has an average temperature of 21°C (71°F), with highs reaching up to 33°C (92°F) and lows dropping to around 6°C (43°F).
JanFebMarAprMayJunJulAugSepOctNovDec303344536675787471584237
Data source: Temperature data for Mattoon 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 Mattoon

In Mattoon in September, the precipitation amount is 67 mm (2.6 in) over the course of 6 days.

September Precipitation Trends in Mattoon

The chart displays monthly precipitation patterns in Mattoon, 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 Mattoon, September typically receives around 67 mm (2.6 inches) of precipitation spread over approximately 6 days.
JanFebMarAprMayJunJulAugSepOctNovDec7879125117135110116123671158965
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in Mattoon

In Mattoon in September humidity is 79%. With an average temperature of 21°C (71°F), this humidity feels like a warm, sticky embrace that can make outdoor activities feel laborious and exhausting. Travelers should be prepared to hydrate frequently and take breaks in shaded areas to fully enjoy their time exploring.

September Average Humidity in Mattoon

This chart illustrates the average monthly humidity levels in Mattoon, 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 Mattoon is approximately 79%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec84%82%84%83%80%83%82%83%79%79%88%87%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Mattoon

In Mattoon 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 Mattoon.

Maximum UV Index Levels in Mattoon for September

The chart shows the monthly maximum UV Index (UVI) for Mattoon 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 Mattoon typically reaches 8, which falls under the very high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec356910111098643
Data source: Mattoon 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 Mattoon Compares to Other Months

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

This table compares monthly weather conditions in Mattoon, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather-1°C (30°F)78 mm (3.1 inches)84%moderate
February Weather1°C (33°F)79 mm (3.1 inches)82%moderate
March Weather7°C (44°F)125 mm (4.9 inches)84%high
April Weather12°C (53°F)117 mm (4.6 inches)83%very high
May Weather19°C (66°F)135 mm (5.3 inches)80%very high
June Weather24°C (76°F)110 mm (4.3 inches)83%extreme
July Weather25°C (78°F)116 mm (4.6 inches)82%very high
August Weather24°C (75°F)123 mm (4.8 inches)82%very high
September Weather21°C (71°F)67 mm (2.6 inches)79%very high
October Weather14°C (58°F)115 mm (4.5 inches)79%high
November Weather6°C (42°F)89 mm (3.5 inches)88%moderate
December Weather3°C (37°F)65 mm (2.6 inches)87%moderate

Compare Mattoon's Climate with Cities Worldwide