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September Weather in Lewistown, United States

Last updated: June 24, 2025

In September, the average temperature in Lewistown, United States hovers around 14°C (57°F). Expect a wide range, with minimums dropping to -3°C (28°F) and maximums soaring to 34°C (94°F). Precipitation is moderate, totaling 45 mm (1.8 in) over 6 days, accompanied by an average humidity of 67%. Stay prepared for the variability of the season!

September Temperature in Lewistown

In September in Lewistown, the average temperature is 14°C (57°F). Maximum can reach 34°C (94°F) and minimum can be as low as -3°C (28°F). Be prepared for a wide range of temperatures when traveling, so pack accordingly!

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

The chart illustrates September temperature patterns in Lewistown, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Lewistown, September typically has an average temperature of 14°C (57°F), with highs reaching up to 34°C (94°F) and lows dropping to around -3°C (28°F).
JanFebMarAprMayJunJulAugSepOctNovDec251832385060696757413426
Data source: Temperature data for Lewistown 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 Lewistown

In Lewistown in September, the precipitation amount is 45 mm (1.8 in) over the course of 6 days.

September Precipitation Trends in Lewistown

The chart displays monthly precipitation patterns in Lewistown, 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 Lewistown, September typically receives around 45 mm (1.8 inches) of precipitation spread over approximately 6 days.
JanFebMarAprMayJunJulAugSepOctNovDec254329768480303145453431
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in Lewistown

In Lewistown in September, humidity is 67%. With an average temperature of 14°C (57°F), this humidity feels like a cool, refreshing mist that invigorates your senses, making it quite pleasant for traveling, though a light jacket is recommended as the moisture in the air can create a brisk atmosphere.

September Average Humidity in Lewistown

This chart illustrates the average monthly humidity levels in Lewistown, 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 Lewistown is approximately 67%, offering insight into how humid the weather typically is during this month.
JanFebMarAprMayJunJulAugSepOctNovDec81%85%77%72%75%78%79%76%67%69%78%85%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Lewistown

In Lewistown 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 Lewistown.

Maximum UV Index Levels in Lewistown for September

The chart shows the monthly maximum UV Index (UVI) for Lewistown 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 Lewistown typically reaches 8, which falls under the very high exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec24589101098532
Data source: Lewistown 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 Lewistown Compares to Other Months

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

This table compares monthly weather conditions in Lewistown, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather-4°C (25°F)25 mm (1.0 inches)81%low
February Weather-8°C (18°F)43 mm (1.7 inches)85%moderate
March Weather0°C (32°F)29 mm (1.2 inches)77%moderate
April Weather3°C (38°F)76 mm (3.0 inches)72%very high
May Weather10°C (50°F)84 mm (3.3 inches)75%very high
June Weather16°C (61°F)80 mm (3.2 inches)78%very high
July Weather20°C (69°F)30 mm (1.2 inches)79%very high
August Weather19°C (67°F)31 mm (1.2 inches)76%very high
September Weather14°C (57°F)45 mm (1.8 inches)67%very high
October Weather5°C (42°F)45 mm (1.8 inches)69%moderate
November Weather1°C (34°F)34 mm (1.3 inches)78%moderate
December Weather-3°C (27°F)31 mm (1.2 inches)85%low

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