nomadseason

September Weather in Collinsville, United States

Last updated: June 24, 2025

In September, the average temperature in Collinsville, United States hovers around 25°C (78°F), offering a pleasant climate. However, temperatures can range from a chilly 10°C (50°F) to a sweltering 36°C (98°F). Visitors should also prepare for an average precipitation of 121 mm (4.7 in) over the course of 7 days, while enjoying an average humidity level of 65%.

September Temperature in Collinsville

In September in Collinsville, the average temperature is 25°C (78°F). Maximums can reach 36°C (98°F), and minimums can drop as low as 10°C (50°F). Travelers should be prepared for warm days and cooler evenings during this time.

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

The chart illustrates September temperature patterns in Collinsville, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Collinsville, September typically has an average temperature of 25°C (78°F), with highs reaching up to 36°C (98°F) and lows dropping to around 10°C (50°F).
JanFebMarAprMayJunJulAugSepOctNovDec454758637380848378665550
Data source: Temperature data for Collinsville generated using information from the Copernicus Climate Change Service.
Choose your preferred temperature unit
The average of daily temperatures (24 hours) calculated across all days in the month.

September Precipitation in Collinsville

In Collinsville in September, the precipitation amount is 121 mm (4.7 in) over the course of 7 days.

September Precipitation Trends in Collinsville

The chart displays monthly precipitation patterns in Collinsville, 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 Collinsville, September typically receives around 121 mm (4.7 inches) of precipitation spread over approximately 7 days.
JanFebMarAprMayJunJulAugSepOctNovDec578811510613910548941211435359
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
Choose your preferred precipitation unit

September Humidity in Collinsville

In Collinsville in September, humidity is 65%. With an average temperature of 25°C (78°F), this humidity feels like a warm, enveloping shawl that makes traveling slightly more strenuous, requiring frequent breaks to stay refreshed and hydrated.

September Average Humidity in Collinsville

This chart illustrates the average monthly humidity levels in Collinsville, 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 Collinsville is approximately 65%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec80%79%78%78%81%78%73%66%65%72%82%87%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Collinsville

In Collinsville in September, the maximum UV index reaches 10, which corresponds to a very high Exposure Category. With a time to burn of just 15 minutes, it's crucial to take precautions. For more detailed information, you can check the Hourly UV Index in Collinsville.

Maximum UV Index Levels in Collinsville for September

The chart shows the monthly maximum UV Index (UVI) for Collinsville 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 Collinsville typically reaches 10, which falls under the very high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec468101111111110864
Data source: Collinsville 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 Collinsville Compares to Other Months

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

This table compares monthly weather conditions in Collinsville, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather7°C (45°F)57 mm (2.2 inches)80%moderate
February Weather8°C (47°F)88 mm (3.5 inches)79%high
March Weather15°C (59°F)115 mm (4.5 inches)78%very high
April Weather17°C (64°F)106 mm (4.2 inches)78%very high
May Weather23°C (73°F)138 mm (5.5 inches)81%extreme
June Weather27°C (81°F)105 mm (4.1 inches)78%extreme
July Weather29°C (84°F)47 mm (1.9 inches)73%extreme
August Weather29°C (84°F)94 mm (3.7 inches)66%extreme
September Weather25°C (78°F)121 mm (4.7 inches)65%very high
October Weather19°C (66°F)143 mm (5.6 inches)72%very high
November Weather13°C (55°F)53 mm (2.1 inches)82%high
December Weather10°C (50°F)59 mm (2.3 inches)87%moderate

Compare Collinsville's Climate with Cities Worldwide