Last updated: June 24, 2025
In September, the average temperature in Lewiston, United States hovers around 16°C (60°F), providing a pleasant climate for visitors. However, be prepared for a temperature range that can dip to a chilly -2°C (29°F) and soar up to a sweltering 34°C (94°F). Rainfall is not uncommon, with an average precipitation of 69 mm (2.7 in) over 11 days. The air tends to be quite humid, with an average humidity level of 79%, making the atmosphere feel quite lively!
In September in Lewiston, the average temperature is 16°C (60°F). Maximum temperatures can reach 34°C (94°F), while minimums can drop as low as -2°C (29°F). This varied climate encourages travelers to pack accordingly, ensuring comfort whether enjoying warm days or chilly nights.
In Lewiston in September, the total precipitation amount is 69 mm (2.7 in) spread across 11 days.
In Lewiston in September humidity is 79%. With an average temperature of 16°C (60°F), this humidity feels like a warm, damp blanket enveloping you, making outdoor activities a bit uncomfortable and requiring frequent breaks to stay cool and refreshed while traveling.
In Lewiston in September, the maximum UV index is 7, which corresponds to the high Exposure Category. This means that the time to burn is approximately 25 minutes. For more 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 | -7°C (20°F) | 49 mm (1.9 inches) | 92% | low |
| February Weather | -6°C (21°F) | 55 mm (2.1 inches) | 91% | moderate |
| March Weather | -1°C (30°F) | 55 mm (2.2 inches) | 87% | moderate |
| April Weather | 5°C (41°F) | 94 mm (3.7 inches) | 85% | high |
| May Weather | 13°C (55°F) | 101 mm (4.0 inches) | 79% | very high |
| June Weather | 18°C (65°F) | 105 mm (4.1 inches) | 75% | very high |
| July Weather | 21°C (70°F) | 87 mm (3.4 inches) | 75% | very high |
| August Weather | 20°C (68°F) | 95 mm (3.7 inches) | 75% | very high |
| September Weather | 16°C (60°F) | 69 mm (2.7 inches) | 79% | high |
| October Weather | 9°C (48°F) | 116 mm (4.6 inches) | 85% | moderate |
| November Weather | 1°C (34°F) | 62 mm (2.4 inches) | 88% | moderate |
| December Weather | -3°C (27°F) | 64 mm (2.5 inches) | 89% | low |