Which park should you choose?
Sri Lanka has fourteen parks worth a safari and they are genuinely different days out. The park decides what you see far more than the jeep does, so it is worth a few minutes before you book. Here is the short version.
You want the best chance of a leopard
Yala, and it is not close. It holds one of the densest leopard populations on earth and Block 1 is the most productive stretch of it. The cost is company: the block runs a daily vehicle quota that fills in peak season, and thirty jeeps at a single sighting is normal. Wilpattu is the quieter alternative with lower odds and far better encounters when they happen.
You want to be certain you see elephants
Udawalawe. Several hundred elephants live there permanently rather than passing through on migration, and the open grassland means they are visible at distance rather than hidden in scrub. It is the one park in Sri Lanka where a sighting is close to certain on any session at any time of year, which also makes it the easiest first safari.
You want the elephant gathering
Minneriya, Kaudulla and Hurulu are one system rather than three choices. Herds move between them following water and grazing: roughly Minneriya from July to September, Kaudulla from October to November, Hurulu from December to January. Book a driver who works all three gates and decide in the last day or two, because a park name fixed months ahead is the most common way visitors miss it.
You are travelling with children
Udawalawe first, then Bundala. Both have shorter sessions, gentler tracks, a later start than Yala's pre dawn queue, and visible wildlife throughout rather than long waits hoping something appears. Yala can be a hard four hours for a young child who sees nothing for the first two.
You care about birds
Bundala is a Ramsar wetland of lagoons and dunes near Hambantota and the most reliable place in the country for greater flamingos, which arrive around September and stay through to March or April. Kumana is the other serious birding park, where the villu becomes a nesting colony of thousands of waterbirds between roughly April and July.
You want somewhere without other jeeps
Wasgamuwa, Maduru Oya, Lunugamvehera or Gal Oya. Fewer vehicles means wildlife that behaves naturally rather than ignoring you, and it means lower odds on any given drive. Gal Oya is the outlier worth knowing about: it is the only park in Sri Lanka explored by boat, and the only place you can watch wild elephants swim between islands.
Safari seasons across the island
Sri Lanka has two monsoons hitting opposite coasts at opposite times, so there is no single best month for a safari. What matters is the dry season in the region you are visiting, because as the smaller water sources fail the animals concentrate on what is left and the scrub thins out.
In the south, Yala, Bundala and Lunugamvehera are strongest from roughly February to July, with the back half of that window generally the best for leopards. Yala has historically closed for several weeks around September, so check the dates before committing to travel then.
Wilpattu in the northwest runs on a different rainfall pattern and is good from around February to October. In the Cultural Triangle the gathering builds through the dry months and moves between Minneriya, Kaudulla and Hurulu from July into January. Udawalawe is the exception that works year round, because its elephants are resident rather than migratory.
The green months are not a write off. Fewer jeeps, better landscape, and the migrant birds arrive from November. Sightings are harder because animals no longer need to come to a handful of waterholes, but a quiet park in good light is a real trip that most visitors never consider.