Rinjani's Two Seasons
Lombok, like much of Indonesia, experiences two distinct seasons: the dry season (roughly May to October) and the wet season (November to April). For trekking Mount Rinjani, this distinction is critical — it determines whether trails are safe, permits are available, and whether you'll enjoy clear summit views or wade through rain and mud.
The Dry Season: May to October (Recommended)
This is the primary trekking window for Rinjani and the period when the national park is fully open to visitors. Conditions during these months are generally favourable, though there are differences within this period worth knowing.
May – June: Shoulder Season (Excellent)
Often considered the sweet spot for Rinjani trekking. The dry season has just begun, vegetation is lush and green from the rains, trails are not yet overcrowded, and temperatures are comfortable. Mornings are frequently clear with outstanding summit views.
- ✅ Fewer crowds than July–August
- ✅ Lush, photogenic landscapes
- ✅ Comfortable temperatures
- ⚠️ Occasional afternoon showers still possible in May
July – August: Peak Season (Busy but Reliable)
This is the most popular window, coinciding with Northern Hemisphere summer holidays. Trails can be busy, particularly on the Sembalun route. Book permits and operators well in advance — sometimes months ahead. Weather is at its most stable, and summit visibility is typically excellent.
- ✅ Most reliable weather conditions
- ✅ Highest chance of clear summit views
- ⚠️ Busiest trail conditions
- ⚠️ Higher demand for guides and permits — book early
September – October: Late Dry Season (Good)
Crowds begin to thin after the European summer. Weather remains mostly dry, though the volcanic dust on upper trails becomes thick and fine by September, making gaiters and a dust mask useful. October may see the first rains return toward month's end.
- ✅ Fewer trekkers on the trail
- ✅ Good weather still likely
- ⚠️ Dusty conditions on upper slopes
- ⚠️ Weather can become unpredictable in late October
The Wet Season: November to April (Not Recommended)
Rinjani National Park officially closes to trekking during the peak wet season, typically from around December through to the end of March (exact dates vary by year — always confirm with the park authority). Even during the shoulder months of November and April, trekking conditions deteriorate significantly.
- ❌ Trail closures for safety: landslide and flash flood risk
- ❌ Permits not issued during official closure period
- ❌ Cloud cover typically obscures summit and crater views
- ❌ Trails become slippery and dangerous, especially on steep descents
No responsible operator will take trekkers up during the official closure. If someone offers to do so, walk away — it is illegal and genuinely dangerous.
Month-by-Month Quick Reference
| Month | Season | Trek Status | Conditions |
|---|---|---|---|
| January | Wet | ❌ Closed | Heavy rain, dangerous |
| February | Wet | ❌ Closed | Heavy rain, dangerous |
| March | Wet | ❌ Closed | Wet, slowly easing |
| April | Transitional | ⚠️ Variable | Park may begin re-opening |
| May | Dry | ✅ Open | Excellent, lush |
| June | Dry | ✅ Open | Excellent |
| July | Dry | ✅ Open | Best, busy |
| August | Dry | ✅ Open | Best, busy |
| September | Dry | ✅ Open | Good, dusty |
| October | Dry | ✅ Open | Good, easing off |
| November | Wet | ⚠️ Risky | Rains beginning |
| December | Wet | ❌ Closed | Heavy rain |
Our Recommendation
For most trekkers, June or early September offers the best combination of good weather, manageable crowds, and lush scenery. If summiting the peak is your priority and you want the clearest possible skies, aim for July or August and book your operator early.