Last updated: June 24, 2025
In Lewiston, United States, the average temperature in September hovers around 15°C (59°F), providing a mild climate. However, be prepared for a range of temperatures, as the minimum can dip to -2°C (30°F) while the maximum may soar to 32°C (90°F). Expect 36 mm (1.4 in) of precipitation over 5 days, contributing to an average humidity of 46%. Whether you're enjoying the warmth or bundled up against the chill, this month's weather offers a diverse experience.
In September in Lewiston, the average temperature is 15°C (59°F). Maximums can reach 32°C (90°F), while minimums can be as low as -2°C (30°F). Be prepared for a wide range of temperatures during your travels, ensuring you pack accordingly for both warm and cool weather.
In Lewiston in September, the precipitation amount is 36 mm (1.4 in) over the course of 5 days.
In Lewiston in September humidity is 46%. With an average temperature of 15°C (59°F), this humidity feels like a refreshing embrace, making it comfortable for traveling, as the cool air balances perfectly with the moderate moisture, creating an inviting atmosphere for exploration.
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.
UV Risk Categories
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.
| Temperature | Precipitation | Humidity | UV | |
|---|---|---|---|---|
| January Weather | -5°C (23°F) | 68 mm (2.7 inches) | 91% | moderate |
| February Weather | -4°C (25°F) | 89 mm (3.5 inches) | 92% | moderate |
| March Weather | 1°C (34°F) | 63 mm (2.5 inches) | 84% | very high |
| April Weather | 4°C (40°F) | 78 mm (3.1 inches) | 74% | very high |
| May Weather | 9°C (49°F) | 66 mm (2.6 inches) | 62% | extreme |
| June Weather | 17°C (62°F) | 31 mm (1.2 inches) | 56% | extreme |
| July Weather | 22°C (71°F) | 17 mm (0.7 inches) | 44% | extreme |
| August Weather | 20°C (69°F) | 23 mm (0.9 inches) | 37% | extreme |
| September Weather | 15°C (59°F) | 36 mm (1.4 inches) | 46% | very high |
| October Weather | 6°C (43°F) | 49 mm (1.9 inches) | 67% | high |
| November Weather | 0°C (33°F) | 56 mm (2.2 inches) | 84% | moderate |
| December Weather | -5°C (23°F) | 59 mm (2.3 inches) | 88% | moderate |