September Weather in Lewiston, United States

Last updated: June 24, 2025

In September, the average temperature in Lewiston, United States is a pleasant 20°C (68°F). Expect a minimum of 2°C (35°F) on cooler days, while highs can reach up to 38°C (101°F). During this month, precipitation is light, with an average of just 12 mm (0.5 in) over 2 days, and humidity levels hover around 62%. Enjoy the variety that this climate brings!

September Temperature in Lewiston

In September in Lewiston, the average temperature is 20°C (68°F). Maximums can reach 38°C (101°F) and minimums can be as low as 2°C (35°F). This makes Lewiston an ideal destination for travelers seeking pleasant weather with the potential for both warm days and cooler nights.

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

The chart illustrates September temperature patterns in Lewiston, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Lewiston, September typically has an average temperature of 20°C (68°F), with highs reaching up to 38°C (101°F) and lows dropping to around 2°C (35°F).

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

September Precipitation in Lewiston

In Lewiston in September, the precipitation amount is 12 mm (0.5 in) over the course of 2 days.

September Precipitation Trends in Lewiston

The chart displays monthly precipitation patterns in Lewiston, 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 Lewiston, September typically receives around 12 mm (0.5 inches) of precipitation spread over approximately 2 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 Lewiston

In Lewiston in September, humidity is 62%. With an average temperature of 20°C (68°F), this humidity feels like a warm, balmy embrace that can make outdoor activities enjoyable in the early morning and late afternoon, but can become quite stifling during the midday heat, making it advisable to stay hydrated and take breaks in shaded areas while traveling.

September Average Humidity in Lewiston

This chart illustrates the average monthly humidity levels in Lewiston, 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 Lewiston is approximately 62%, 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 Lewiston

In Lewiston in September, the maximum UV index is 9, which corresponds to a very high Exposure Category. The time to burn is just 15 minutes, so it's essential to take precautions. For detailed information, you can check the Hourly UV Index in Lewiston.

Maximum UV Index Levels in Lewiston for September

The chart shows the monthly maximum UV Index (UVI) for Lewiston 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 Lewiston typically reaches 9, which falls under the very high exposure category.

Data source: Lewiston 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 Lewiston Compares to Other Months

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

This table compares monthly weather conditions in Lewiston, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
	Temperature	Precipitation	Humidity	UV
January Weather	4°C (40°F)	163 mm (6.4 inches)	86%	moderate
February Weather	5°C (41°F)	156 mm (6.1 inches)	85%	moderate
March Weather	7°C (44°F)	137 mm (5.4 inches)	85%	high
April Weather	11°C (51°F)	82 mm (3.2 inches)	82%	very high
May Weather	15°C (59°F)	62 mm (2.4 inches)	81%	extreme
June Weather	20°C (69°F)	15 mm (0.6 inches)	79%	extreme
July Weather	25°C (77°F)	2 mm (0.1 inches)	70%	extreme
August Weather	24°C (76°F)	4 mm (0.1 inches)	60%	very high
September Weather	20°C (68°F)	12 mm (0.5 inches)	62%	very high
October Weather	13°C (56°F)	52 mm (2.0 inches)	72%	high
November Weather	8°C (46°F)	97 mm (3.8 inches)	87%	moderate
December Weather	4°C (39°F)	118 mm (4.6 inches)	86%	moderate