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September Weather in Waterloo, United States

Last updated: June 24, 2025

In September, the average temperature in Waterloo, United States is a pleasant 22°C (73°F). However, temperatures can vary significantly, with a minimum of 8°C (46°F) and a maximum reaching 34°C (94°F). Expect 66 mm (2.6 in) of precipitation spread over approximately 7 days, and a cozy average humidity level of 76%, making it an ideal time for a refreshing getaway!

September Temperature in Waterloo

In September in Waterloo, the average temperature is 22°C (73°F). The maximum can reach 34°C (94°F), and the minimum can be as low as 8°C (46°F). This makes Waterloo an ideal destination for travelers seeking a mild climate with the option for both warm days and cooler evenings.

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

The chart illustrates September temperature patterns in Waterloo, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Waterloo, September typically has an average temperature of 22°C (73°F), with highs reaching up to 34°C (94°F) and lows dropping to around 8°C (46°F).
JanFebMarAprMayJunJulAugSepOctNovDec343748566777807772594540
Data source: Temperature data for Waterloo 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 Waterloo

In Waterloo in September, the precipitation amount is 66 mm (2.6 in) over a period of 7 days.

September Precipitation Trends in Waterloo

The chart displays monthly precipitation patterns in Waterloo, 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 Waterloo, September typically receives around 66 mm (2.6 inches) of precipitation spread over approximately 7 days.
JanFebMarAprMayJunJulAugSepOctNovDec79871361421498789123661097568
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in Waterloo

In Waterloo in September, humidity is 76%. With an average temperature of 22°C (73°F), this humidity feels like a warm embrace that envelops you, making travel both refreshing and slightly steamy, as the air clings warmly to your skin.

September Average Humidity in Waterloo

This chart illustrates the average monthly humidity levels in Waterloo, 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 Waterloo is approximately 76%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec82%80%80%80%82%83%81%80%76%76%85%86%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Waterloo

In Waterloo in September, the maximum UV index is 9, which corresponds to a very high Exposure Category. The time to burn is just 15 minutes, so it's essential to take precautions. For detailed information, you can check the Hourly UV Index in Waterloo.

Maximum UV Index Levels in Waterloo for September

The chart shows the monthly maximum UV Index (UVI) for Waterloo 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 Waterloo typically reaches 9, which falls under the very high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec3579101110109753
Data source: Waterloo 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 Waterloo Compares to Other Months

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

This table compares monthly weather conditions in Waterloo, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather1°C (34°F)79 mm (3.1 inches)82%moderate
February Weather3°C (37°F)87 mm (3.4 inches)80%moderate
March Weather9°C (48°F)136 mm (5.4 inches)80%high
April Weather13°C (56°F)142 mm (5.6 inches)80%very high
May Weather20°C (68°F)149 mm (5.9 inches)82%very high
June Weather25°C (77°F)87 mm (3.4 inches)83%extreme
July Weather27°C (80°F)89 mm (3.5 inches)81%very high
August Weather25°C (77°F)123 mm (4.8 inches)80%very high
September Weather22°C (73°F)66 mm (2.6 inches)76%very high
October Weather15°C (60°F)109 mm (4.3 inches)76%high
November Weather7°C (45°F)75 mm (2.9 inches)85%moderate
December Weather4°C (40°F)68 mm (2.7 inches)86%moderate

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