January is the wet season in Indonesia, and many of the islands get hit with rain—making it a less-than-ideal time if you're seeking sunshine and beach-going activities. That said, it usually only rains for a small portion of the day and there are plenty of locations where the precipitation is lighter. Best of all, there are hardly any people around, so you won't have to contend with the crowds that swarm beach resorts during other times of the year.
March is a rainy month in Indonesia, and large swaths of the country get pummeled with tropical storms. Although Bali remains less affected, many of the other islands are susceptible to flooding and washed-out roads. That said, the rain usually comes in short, intense bursts followed by sunshine and blue skies. Plus, the crowd sizes are small so if you don't mind a little bit of rain, it can actually be a great time of year for a visit.
Indonesia is a massive country comprised of many regions and thousands of islands spread from east to west across the Indian and Pacific oceans. It's also primarily tropical. Other than a wet and dry season, the temperatures here change little throughout the year. So planning the perfect Indonesian getaway is as simple as picking the suitable months to avoid the heavier rains.
April is a shoulder season in Indonesia when the country shifts from its wet, rainy low-season into a more pleasant dry season that's sunny and full of tourists. It still gets a fair amount of rain—in fact, some consider April to still be wet season. However, you'll find far more dry days than earlier in the year and there are hardly any tourists, which makes it a great "best of both worlds" destination.
July is a month when Indonesia is at its absolute best. The weather is dry, the ocean is warm, and the beaches are full of people surfing, snorkeling, and playing in the sun. It's the perfect time to hike one of the volcanos, explore the many temples, and wander through the bustling street markets. It's high season, and hence more crowded and expensive. Still, if you're seeking a vacation with great weather and plenty of activities, it won't disappoint.