October to April is the only comfortable window for visiting. Winter temperatures hover between 15°C and 25°C, making a long walk around the archaeological site pleasant. From May through September the heat is extreme — 40°C and above — and the site has almost no shade. There is nothing to stop you going in summer if you arrive early and leave before 10am, but it will be an uncomfortable experience.
Bird-watchers should aim for November to February, when flamingos and migratory waders are most numerous in the coastal lagoons.