Weather data last updated: August 01, 2026 at 07:47 AM UTC
Mount Si Trail — 66/100 Caution
Manageable with preparation. Plan accordingly.
- Weather Comfort: 6/40
- Safety Risk: 30/30
- Seasonal Match: 20/20
- Daylight Window: 10/10
Mount Si Trail in Washington is a hard-rated route that demands respect — 8.0 miles with significant elevation change up to 4,167 ft. Our daily Suitability Score helps you pick the window with the best conditions, but this trail requires self-sufficiency and solid navigation skills.
Today’s Conditions at a Glance
High-Elevation Considerations
Summit temperatures can feel 11°F cooler than the trailhead (roughly 3.5°F per 1,000 ft gained). Above 8,000 ft, watch for altitude sickness symptoms: headache, nausea, and shortness of breath. Descend if symptoms worsen.
- Start early to avoid afternoon storms on exposed ridges
- Pack insulating layers even in summer
- Carry extra water — dehydration accelerates at altitude
Seasonal Guide
- Spring: Spring (Washington): Snow may linger above 6,000 ft through May. Muddy lower sections are common. Layers essential — mornings can be near freezing.
- Summer: Summer: Start before 8 AM to beat heat and afternoon thunderstorms. Afternoon temps at 4,167 ft can still be comfortable, but exposed sections get hot quickly. Lightning risk peaks on exposed ridges after noon.
- Fall: Fall: Often the best hiking season — stable weather, fewer crowds. Shorter days mean plan turnaround times carefully after September.
- Winter: Winter: Limited daylight and potential snow/ice above 5,000 ft. Check our daily score; many trails remain accessible with traction devices.
What to Pack
- Sturdy hiking boots with ankle support
- 2+ liters of water (more in heat or for long routes)
- Snacks and electrolytes
- Sunscreen, hat, and sunglasses
- First-aid kit and whistle
- Fully charged phone + offline map backup
- Insulating mid-layer and waterproof shell
7-Day Forecast & Hiking Suitability
| Date | High/Low | Rain | Wind | Score | Rating |
|---|---|---|---|---|---|
| 2026-07-30 | 61°F / 43°F | 2% | 8 mph | 66 | Caution |
| 2026-07-31 | 67°F / 49°F | 0% | 9 mph | 73 | Good |
| 2026-08-01 | 55°F / 45°F | 49% | 14 mph | 50 | Caution |
| 2026-08-02 | 57°F / 41°F | 12% | 11 mph | 66 | Caution |
| 2026-08-03 | 68°F / 39°F | 0% | 7 mph | 73 | Good |
| 2026-08-04 | 77°F / 47°F | 0% | 6 mph | 78 | Good |
| 2026-08-05 | 78°F / 49°F | 1% | 6 mph | 78 | Good |
Trail Information
- Location: Mount Si Natural Resources, WA
- Length: 8.0 miles
- Elevation: 4167 ft
- Difficulty: Hard
Frequently Asked Questions
What is the best time to hike Mount Si Trail?
Review our 7-day suitability scores and seasonal match rating. Elevation and WA climate vary significantly by month.
Is Mount Si Trail safe to hike today?
Check today’s Suitability Score above. This is informational only — always confirm with official park sources before hiking.
What should I wear on Mount Si Trail?
Plan layers based on forecast highs/lows and elevation. Waterproof gear if rain probability exceeds 40%.
Disclaimer: For informational purposes only. Not professional outdoor safety advice. Always check official NPS/USFS sources before hiking. Weather data by Open-Meteo. Trail data © OpenStreetMap contributors.