- The summit is roughly 5–10°C colder than Jeju City, and windier.
- Trails stay open unless severe weather occurs. The exact limits aren't published, so rangers decide on the day.
- Check the official park site (visithalla.jeju.go.kr) the week you go for the current trail status.
1. Why the Jeju City forecast misleads
Hallasan generates its own weather, and the summit can turn faster than what you see from the coast. A clear morning in the city doesn't mean a clear summit. Treat any forecast as a guide only, and be ready to turn back.
2. What to wear
- A windproof jacket, whatever the temperature at the start.
- A warm layer and a rain shell. Wind chill makes the summit feel colder than the numbers.
- Proper hiking shoes. The upper sections are loose, muddy volcanic rock.
- Crampons in winter: see the full booking and trail guide.
3. Check trail status before you book and again before you go
Closure windows for sections of the trails can move, and trails can close in severe weather. Check visithalla.jeju.go.kr before you plan a summit day, and again the week you go. I could not find published weather limits for closures, so don't rely on a specific number from any blog, including this one.
4. If the weather turns
Turn back rather than push for the summit. If you can't go, cancel your reservation before your slot ends so someone else can take it. No-shows are banned from booking for 3 months. Details are in the booking guide.
Rather not worry about conditions and logistics? A guided hike handles planning and transport.
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