Weather ranges around 20 to 25 degrees celsius, though it feels much cooler when a breeze blows (at least the air doesn't feel furnace-like as it is in Singapore).
Crisp mornings, warm afternoons (bring sunblock - you may get burnt if you aren't careful), chilly nights.
I spent the whole trip in T-shirts and bermudas, though I saw some people togged out in sweaters......