Olympic National Park weather in September
September in Olympic National Park: cool, rainy, with clean air — an excellent time to visit.
#4 of 12 months in Olympic National Park · #311 of 604 destinations to visit in September · comfort 80/100 (tier A)
Updated June 2026 · climate normals from ERA5 reanalysis
Olympic National Park climate normals — September
| Daytime high | 16°C / 60°F | 🙂 cool |
|---|---|---|
| Nighttime low | 6°C / 44°F | |
| Feels like (high) | 14°C / 57°F | |
| Rainfall | 146 mm / 5.7 in | 🌧 rainy |
| Rainy days | 12 days | |
| Humidity | 70% | 💧 humid |
| Dew point | 4°C / 39°F | |
| Sunshine | 9.4 h/day | |
| Daylight | 12.6 h | |
| Wind | 9 km/h / 6 mph | |
| Snowfall | 0.1 cm / 0 in | |
| Air quality (US AQI) | 31 | 🍃 good |
Monthly averages from ERA5 reanalysis. AQI is the mean US Air Quality Index for the month.
Where is Olympic National Park?
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Olympic National Park in September — FAQ
- Is September a good time to visit Olympic National Park?
- September in Olympic National Park: cool, rainy, with clean air — an excellent time to visit. It ranks #4 of 12 months for Olympic National Park on SeasonMap's comfort score (80/100).
- What is the weather like in Olympic National Park in September?
- In September, Olympic National Park averages a daily high of 15.5°C and a low of 6.4°C, with about 145.9 mm of rain over roughly 12 rainy days.
- What is the air quality in Olympic National Park in September?
- Olympic National Park has a mean US Air Quality Index of about 31 in September.