Don't go. Trail is dangerous, water is brown, flash flow is real, and guides may refuse to take you.
Mayung Putek Waterfall in December is genuinely not advisable. The 1-1.5 hour trail through the gorge becomes treacherous with mud and slippery rock, the cascade itself runs heavily brown with monsoon sediment, and flash flow from upstream squalls is a real and potentially fatal risk in this enclosed gorge. Local guides regularly refuse to take visitors in December. The Rinjani trek season is over so Sembalun-area logistics are also quieter and harder to coordinate. Wait until April or July.
# Mayung Putek Waterfall in December: A Trip to Skip
December is monsoon at full intensity on Mount Rinjani's eastern slopes, and Mayung Putek becomes a place that local guides actively discourage visiting. The combination of trail conditions, water quality, and genuine flash-flow risk makes this the worst month of the year — not just suboptimal, but actively unsafe in a way that earlier waterfall guides on this site might describe as merely difficult. Mayung Putek's gorge has features that make it specifically dangerous in December.
Most Lombok waterfalls become harder to reach in December because of trail mud and flow strength. Mayung Putek adds a specific structural risk: the gorge below the falls is narrow and the gorge floor sits well below the surrounding terrain. There is nowhere to climb to quickly if upstream flow spikes. The catchment above the falls drains a significant area of Mount Rinjani's eastern flank, and a heavy upstream squall — common in December — can send a flash pulse down the gorge within 30-45 minutes. People have been swept out of the boulder field. This is not a hypothetical risk.
In dry season the same gorge is fine because the catchment can't generate that kind of pulse. In December it can, repeatedly.
The trail itself is the second issue. The descent into the gorge becomes a clay slide in December's continuous wet weather. The roots and rocks that provide footing in dry season turn into slip hazards. The leeches multiply to genuinely unpleasant numbers. Even guides who know the path intimately struggle with the descent in December conditions.
Third, the water is heavily silted. December flow runs the brownest of any month, full of soil and forest debris from the recharging catchment. Swimming is unappealing and you can't see what's beneath you.
The clearest indicator that a place is unsafe in a given month is when the people who depend on tourist income for their livelihood actively turn the work away. In December at Mayung Putek, this is a regular occurrence. Guides who would happily take you in April or July will look at the morning's weather, the upstream cloud pattern, and the recent rainfall and say "not today" — sometimes "not this week."
If a guide refuses, accept the answer and don't try to find another guide. The first refusal is the honest one.
There are narrow windows where a December visit can theoretically work:
Even then, the water will be brown and the experience will be photographically unrewarding. The realistic best case is a difficult walk to a thunderous brown waterfall. That's not a great trip.
December is the quietest month of the year at Mayung Putek, but only because almost nobody comes. Most days see zero visitors. The few that come are usually long-term Lombok residents or hardcore monsoon-season explorers who know what they're doing. There is no crowd to speak of, but solitude isn't enough of a reward to justify the risks.
If a guide will take you:
Sembalun accommodation is at its annual cheapest, with decent homestay rooms at 150-250k IDR per night.
The smart December plan is to visit Sembalun for the valley itself and skip the falls entirely. The valley is at its lush green peak in December — wet-season rice paddies are flooded and planted, the surrounding hills are green with monsoon growth, and the cool altitude (1,150 metres) keeps temperatures pleasant when the coast is sticky.
Things to do in Sembalun in December that don't involve the gorge:
You can have a meaningful 2-3 day Sembalun experience in December without going anywhere near Mayung Putek.
Mayung Putek Waterfall in December is the wrong month for essentially all travellers. The risk-reward calculation doesn't work — even if the visit goes perfectly, you'll see brown water and a difficult trail; if it goes badly, the consequences can be severe. There is no version of this trip that delivers what April or July do.
If you're already in Lombok in December and you have your heart set on a waterfall experience, Sendang Gile and Tiu Kelep on Rinjani's north slopes are the better choice — better infrastructure, shorter approach, less gorge-trap geography. Save Mayung Putek for a return trip in dry season. The falls aren't going anywhere.
If you're committed to Sembalun in December for the valley itself, that's a good trip on its own merits. Just leave the waterfall hike off the itinerary.
Don't go. This isn't standard travel-blog hedging — Mayung Putek in December is a genuinely bad idea, and the local guides are the most honest source on this. They know the gorge intimately, they know how fast the flash flow can come down, and when they say a December day isn't safe they mean it. If you ask three guides and all three refuse, that's the answer. The smart December plan if you're already in Sembalun is to enjoy the valley itself — the rice paddies in their wet-season state are beautiful, the homestays serve great food, and you can do all the village walking you want without entering the gorge. Save the falls for April or July, when the visit will be both safer and more rewarding.