North Cascades National Park weather in September
September in North Cascades National Park: cold, rainy, with clean air — a great time to visit.
#4 of 12 months in North Cascades National Park · #345 of 604 destinations to visit in September · comfort 78/100 (tier B)
Updated June 2026 · climate normals from ERA5 reanalysis
North Cascades National Park climate normals — September
| Daytime high | 12°C / 53°F | 🧥 cold |
|---|---|---|
| Nighttime low | 1°C / 34°F | |
| Feels like (high) | 9°C / 48°F | |
| Rainfall | 102 mm / 4 in | 🌧 rainy |
| Rainy days | 11 days | |
| Humidity | 70% | 💧 humid |
| Dew point | 0°C / 32°F | |
| Sunshine | 8.6 h/day | |
| Daylight | 12.6 h | |
| Wind | 8 km/h / 5 mph | |
| Snowfall | 1.6 cm / 0.6 in | |
| Air quality (US AQI) | 33 | 🍃 good |
Monthly averages from ERA5 reanalysis. AQI is the mean US Air Quality Index for the month.
Where is North Cascades National Park?
Loading map…
North Cascades National Park in September — FAQ
- Is September a good time to visit North Cascades National Park?
- September in North Cascades National Park: cold, rainy, with clean air — a great time to visit. It ranks #4 of 12 months for North Cascades National Park on SeasonMap's comfort score (78/100).
- What is the weather like in North Cascades National Park in September?
- In September, North Cascades National Park averages a daily high of 11.5°C and a low of 1.2°C, with about 102.3 mm of rain over roughly 11 rainy days.
- What is the air quality in North Cascades National Park in September?
- North Cascades National Park has a mean US Air Quality Index of about 33 in September.
- Does it snow in North Cascades National Park in September?
- North Cascades National Park sees roughly 1.6 cm of snowfall in September.