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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 21°C (71°F). Expect a minimum temperature of 5°C (41°F) and a maximum of 35°C (95°F), making for quite the range! Be prepared for some precipitation, as the area typically receives about 81 mm (3.2 in) over the course of 7 days. Additionally, the average humidity sits at a comfortable 76%, adding to the region's unique climate experience.

September Temperature in Lewistown

In September in Lewistown, the average temperature is 21°C (71°F). Maximums can reach 35°C (95°F), while minimums can drop to as low as 5°C (41°F). This variety in temperature makes it essential to pack layers for your trip, ensuring comfort for both warm and cooler moments.

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 21°C (71°F), with highs reaching up to 35°C (95°F) and lows dropping to around 5°C (41°F).
JanFebMarAprMayJunJulAugSepOctNovDec283144526576797571564236
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 81 mm (3.2 in) over a period of 7 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 81 mm (3.2 inches) of precipitation spread over approximately 7 days.
JanFebMarAprMayJunJulAugSepOctNovDec59571151001771059193811145241
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 76%. With an average temperature of 21°C (71°F), this humidity feels like a warm, enveloping blanket, making traveling both refreshing and a bit exhausting, as the air clings to your skin and you often find yourself reaching for water to stay hydrated.

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 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 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.
JanFebMarAprMayJunJulAugSepOctNovDec3579101110108643
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-2°C (29°F)59 mm (2.3 inches)82%moderate
February Weather-1°C (31°F)57 mm (2.2 inches)80%moderate
March Weather7°C (44°F)115 mm (4.5 inches)80%high
April Weather11°C (53°F)100 mm (4.0 inches)80%very high
May Weather18°C (66°F)177 mm (7.0 inches)82%very high
June Weather24°C (76°F)105 mm (4.1 inches)83%extreme
July Weather26°C (79°F)91 mm (3.6 inches)81%very high
August Weather24°C (76°F)93 mm (3.7 inches)80%very high
September Weather21°C (71°F)81 mm (3.2 inches)76%very high
October Weather14°C (57°F)114 mm (4.5 inches)76%high
November Weather5°C (42°F)52 mm (2.1 inches)85%moderate
December Weather2°C (36°F)41 mm (1.6 inches)86%moderate

Compare Lewistown's Climate with Cities Worldwide