September Weather in Lewistown, United States

Last updated: June 24, 2025

In September, the average temperature in Lewistown, United States is a pleasant 21°C (70°F). You'll experience a range of temperatures, with a minimum of 6°C (43°F) and a maximum of 34°C (94°F). Expect 74 mm (2.9 in) of precipitation spread over about 7 days, and prepare for an average humidity level of 78% to round out your experience.

September Temperature in Lewistown

In September in Lewistown, the average temperature is 21°C (70°F), with maximums reaching 34°C (94°F) and minimums dropping as low as 6°C (43°F). This varied climate makes it an ideal destination for travelers looking to experience a mix of warm days and cooler evenings.

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 (70°F), with highs reaching up to 34°C (94°F) and lows dropping to around 6°C (43°F).

Data source: Temperature data for Lewistown generated using information from the Copernicus Climate Change Service.

September Precipitation in Lewistown

In Lewistown in September, the precipitation amount is 74 mm (2.9 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 74 mm (2.9 inches) of precipitation spread over approximately 7 days.

Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.

Choose your preferred precipitation unit

Millimeters (mm) Inches (in)

September Humidity in Lewistown

In Lewistown in September, humidity is 78%. With an average temperature of 21°C (70°F), this humidity feels like a warm, enveloping blanket that can leave travelers feeling sticky and slightly fatigued, making it important to stay hydrated and take frequent breaks from outdoor activities.

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 78%, offering insight into how humid the weather typically is during this month.

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.

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.
	Temperature	Precipitation	Humidity	UV
January Weather	-3°C (27°F)	60 mm (2.4 inches)	81%	moderate
February Weather	-1°C (30°F)	68 mm (2.7 inches)	81%	moderate
March Weather	6°C (42°F)	121 mm (4.8 inches)	81%	high
April Weather	11°C (51°F)	108 mm (4.3 inches)	82%	very high
May Weather	18°C (64°F)	169 mm (6.7 inches)	78%	very high
June Weather	24°C (75°F)	152 mm (6.0 inches)	81%	extreme
July Weather	25°C (78°F)	103 mm (4.0 inches)	79%	very high
August Weather	24°C (75°F)	86 mm (3.4 inches)	77%	very high
September Weather	21°C (70°F)	74 mm (2.9 inches)	78%	very high
October Weather	13°C (56°F)	117 mm (4.6 inches)	78%	high
November Weather	5°C (41°F)	57 mm (2.2 inches)	87%	moderate
December Weather	1°C (35°F)	52 mm (2.0 inches)	84%	low