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September Weather in Tri-City, United States

Last updated: June 24, 2025

In September, the average temperature in Tri-City, United States is a pleasant 17°C (62°F). However, be prepared for a range of weather; temperatures can drop as low as 2°C (35°F) or soar to a sweltering 37°C (100°F). This month typically sees 61 mm (2.4 in) of precipitation spread across 6 days, with an average humidity level around 66%. Make sure to pack accordingly!

September Temperature in Tri-City

In September in Tri-City, the average temperature is 17°C (62°F), with maximums soaring to 37°C (100°F) and minimums dropping to as low as 2°C (35°F). This climate makes it essential for travelers to pack both light clothing for warm days and warmer layers for cooler evenings.

September Weather in Tri-City: Daily Temperature Highs, Lows, and Averages

The chart illustrates September temperature patterns in Tri-City, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Tri-City, September typically has an average temperature of 17°C (62°F), with highs reaching up to 37°C (100°F) and lows dropping to around 2°C (35°F).
JanFebMarAprMayJunJulAugSepOctNovDec404044495562686862524539
Data source: Temperature data for Tri-City 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 Tri-City

In Tri-City in September, the total precipitation amount is 61 mm (2.4 in) spread over a period of 6 days.

September Precipitation Trends in Tri-City

The chart displays monthly precipitation patterns in Tri-City, 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 Tri-City, September typically receives around 61 mm (2.4 inches) of precipitation spread over approximately 6 days.
JanFebMarAprMayJunJulAugSepOctNovDec1401751241126131286167107140
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in Tri-City

In Tri-City in September, humidity is 66%. With an average temperature of 17°C (62°F), this humidity feels like a mild embrace, making it comfortable for exploring, yet slightly sticky, urging travelers to stay hydrated while enjoying the sights.

September Average Humidity in Tri-City

This chart illustrates the average monthly humidity levels in Tri-City, 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 Tri-City is approximately 66%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec84%85%86%83%83%83%78%67%66%77%87%87%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Tri-City

In Tri-City 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 Tri-City.

Maximum UV Index Levels in Tri-City for September

The chart shows the monthly maximum UV Index (UVI) for Tri-City 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 Tri-City typically reaches 8, which falls under the very high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec346810101098632
Data source: Tri-City 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 Tri-City Compares to Other Months

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

This table compares monthly weather conditions in Tri-City, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather5°C (40°F)140 mm (5.5 inches)84%moderate
February Weather4°C (40°F)175 mm (6.9 inches)85%moderate
March Weather7°C (44°F)124 mm (4.9 inches)86%high
April Weather10°C (49°F)112 mm (4.4 inches)83%very high
May Weather13°C (55°F)61 mm (2.4 inches)83%very high
June Weather17°C (62°F)31 mm (1.2 inches)83%very high
July Weather20°C (68°F)2 mm (0.1 inches)78%very high
August Weather20°C (68°F)8 mm (0.3 inches)67%very high
September Weather17°C (62°F)61 mm (2.4 inches)66%very high
October Weather11°C (52°F)67 mm (2.6 inches)77%high
November Weather7°C (45°F)107 mm (4.2 inches)87%moderate
December Weather4°C (39°F)140 mm (5.5 inches)87%low

Compare Tri-City's Climate with Cities Worldwide