The short version
Dry season: April to October. Sunny, calm seas, best diving visibility, biggest crowds in July and August.
Wet season: November to March. Warm rain showers (usually short), fewer visitors, lower prices, still plenty of sunshine between storms.
Best months overall: May, June, and September offer the sweet spot of great weather without peak crowds.
Temperature
The Gili Islands sit just 8 degrees south of the equator, so the temperature is remarkably consistent year-round. Average daytime temperatures range from 27°C to 30°C (80°F to 86°F) almost every day of the year. Nights are warm, typically 24°C to 26°C (75°F to 79°F). You will never need a jacket.
The sea temperature is also consistent: 27°C to 29°C (80°F to 84°F) year-round. This is bath-warm water, ideal for swimming, snorkelling, and diving without a wetsuit.
The dry season (April to October)
The dry season is the best time to visit if you want guaranteed sunshine and calm seas. Rain is rare, skies are mostly clear, and the sea is flat. Diving visibility often exceeds 25 metres. This is when you will get the classic Gili experience: perfect sunsets, glassy water, and easy island hopping.
The trade-off is crowds. July and August are peak tourism months with European school holidays and Australian winter escapes. Trawangan in particular can feel busy, accommodation fills up weeks in advance, and prices for everything increase 20-50%. If you visit in these months, book early.
June, September, and October offer the dry weather of peak season without the crowds. These are arguably the best months to visit.
The wet season (November to March)
The wet season gets a worse reputation than it deserves. Yes, it rains more, but Indonesian tropical rain is usually short, intense, and followed by sunshine. You might get a heavy downpour in the afternoon that clears in 30 minutes, leaving a fresh, beautiful evening. Whole days of rain are uncommon.
The real downsides of wet season are:
- Rougher seas. Fast boat crossings from Bali can be bumpy and occasionally cancelled
- Reduced visibility. Plankton blooms and runoff can reduce underwater visibility to 10-15 metres
- Humidity. It is more humid, though the temperature stays the same
- Mosquitoes. More rain means more mosquitoes, especially inland
The upsides of wet season:
- Cheap. Accommodation and activities can be half the peak season price
- Quiet. You might have whole stretches of beach to yourself
- Atmospheric. Dramatic clouds, vivid greens, moody light for photography
- Local feel. Without the crowds, the islands feel more authentic
Month by month
| Month | Season | Rain | Temp | Notes |
|---|---|---|---|---|
| January | Wet | High | 28°C | Low season. Shorter rain bursts, still plenty of sunshine between them. Fewer crowds. Prices lower. |
| February | Wet | High | 28°C | Wettest month. Rain is still tropical and short-lived. Cheapest accommodation of the year. Good for budget travellers. |
| March | Transition | Moderate | 28°C | End of wet season. Rain tapers off. Diving visibility improving. Great value and few crowds. |
| April | Dry | Low | 28°C | Start of dry season. Visibility excellent. Quiet before the peak. One of the best times to visit. |
| May | Dry | Very low | 28°C | Perfect weather, still quiet. Ideal for diving, snorkelling, and beach time. Prices reasonable. |
| June | Dry | Very low | 27°C | Dry, slightly cooler. High season starts. Book accommodation in advance. |
| July | Dry (Peak) | Minimal | 27°C | Peak season. Crowded, especially Trawangan. Book everything in advance. Prices highest. Weather perfect. |
| August | Dry (Peak) | Minimal | 27°C | Peak of peak season. Lively atmosphere. Everything booked solid. Best diving conditions. |
| September | Dry | Low | 28°C | High season tails off. Still excellent weather, fewer crowds. Sweet spot for many visitors. |
| October | Dry | Low | 28°C | End of dry season. Warm, sunny, quieter. Great month to visit. |
| November | Transition | Moderate | 28°C | Start of wet season. Rain returns but still plenty of sun. Lower prices. |
| December | Wet | High | 28°C | Wet season returns. Christmas/New Year brings a brief spike in visitors. Otherwise quiet. |
When to book
For dry season (April to October): book accommodation and popular dive courses at least a month in advance. For July and August, book 2-3 months ahead, especially if you want specific resorts or dive shops.
For wet season: last-minute bookings are usually fine, and you can often find walk-in deals at accommodation. Still worth booking for Christmas and New Year week when there is a brief spike in visitors.
Packing for the weather
Whatever month you visit, you only need lightweight clothing. A light rain jacket or compact poncho is useful in wet season. A light long-sleeved shirt helps with sun protection and mosquitoes. Everything else (swimwear, shorts, sandals, one or two nicer outfits for dinner) is all you need.