Mount ThielsenMount Thielsen at a Glance
Tips for Visiting Mount Thielsen
- Attempt Mount Thielsen in mid‑summer to early fall when routes are most likely to be free of snow and technical ice; shoulder seasons commonly retain hazardous snowfields.
- Start very early to avoid afternoon thunderstorms common in the Cascades and to give yourself plenty of daylight for the exposed final ridgeline and descent.
- Treat the summit ridge as an alpine scramble: route‑finding and exposure are significant - only go if you have alpine experience and the right gear, and check current mountain conditions with the U.S. Forest Service before heading out.
Things to Do
Nearby Attractions to Mount Thielsen
When to Go
Best Time to Visit Mount Thielsen
Best climbed in summer (July-September) when snow is reduced and hiking routes are most accessible.
Summer hiking season (best)
July-September · 0-20°C
Most snow has melted on lower routes, daylight is long and non-technical hiking access is at its best, though summit sections can remain icy.
Snow/winter conditions
October-June · -15-5°C
Significant snowpack and avalanche/technical alpine conditions prevail - suitable only for experienced winter mountaineers with proper gear.
Weather & Climate near Mount Thielsen
Climate
Mount Thielsen's climate is classified as Subarctic (Dry Summer) - Subarctic (Dry Summer) climate with cool summers (peaking in August) and freezing winters (coldest in December). Temperatures range from -9°C to 19°C. Abundant rainfall (1753 mm/year), wettest in December.
Air Quality:
AQI 30
Good
Temperature & Rainfall
Temperature Range
19°
Warmest Month
-9°
Coldest Month
Monthly Conditions
| Month | Comfort | Temp | Feels | Rain | Sky | Humidity | Wind | UV | Daylight |
|---|---|---|---|---|---|---|---|---|---|
| January | - | -8° - 1° | -9° | 264 mm | - | - | 4.1 m/s | - | - |
| February | - | -8° - 1° | -9° | 212 mm | - | - | 4.0 m/s | - | - |
| March | - | -8° - 2° | -8° | 200 mm | - | - | 3.9 m/s | - | - |
| April | - | -7° - 4° | -6° | 136 mm | - | - | 3.8 m/s | - | - |
| May | - | -4° - 8° | -2° | 93 mm | - | - | 3.7 m/s | - | - |
| June | - | -1° - 12° | 3° | 60 mm | - | - | 3.7 m/s | - | - |
| July | - | 3° - 18° | 10° | 28 mm | - | - | 3.6 m/s | - | - |
| August | - | 3° - 19° | 11° | 33 mm | - | - | 3.4 m/s | - | - |
| September | - | 1° - 16° | 6° | 59 mm | - | - | 3.5 m/s | - | - |
| October | - | -2° - 11° | 1° | 120 mm | - | - | 3.6 m/s | - | - |
| November | - | -7° - 3° | -7° | 269 mm | - | - | 4.0 m/s | - | - |
| December | - | -9° - 1° | -10° | 279 mm | - | - | 4.1 m/s | - | - |