The dry season from roughly April to October is the best time to visit, with sunny days, calmer seas for snorkelling and diving, and safer, clearer conditions for trekking Mount Rinjani, whose main routes usually close in the wet months. July and August are the busiest and driest, while the shoulder months of April to June and September to October balance good weather with fewer crowds. The wet season from November to March brings heavy downpours, rougher crossings and green, quiet landscapes.
Mount Rinjani is a serious high-altitude trek with cold nights, steep scree and changeable weather, and it is an active volcano subject to closures. Go only with a licensed guide and proper gear, follow official park status, and never attempt the summit alone or off-season.
The seas around the Gili Islands and the south-coast beaches can have strong currents and boat traffic. Snorkel and swim within marked or sheltered areas, check conditions locally, take diving only with reputable operators, and be cautious of currents when boats are moving nearby.
Scooter accidents are the most common cause of injury for visitors, on roads that range from smooth to rough with informal driving. Wear a helmet, ride slowly and defensively, avoid riding at night or in the rain, and make sure your travel insurance covers scooter use.
Lombok is mostly Muslim and more conservative than Bali, especially in villages and towns away from the beach resorts. Dress modestly off the sand, take extra care around prayer times and during Ramadan, and ask before photographing people or ceremonies.