October to February is the best window. The monsoon ends by early October and the Western Ghats landscape is at its most lush and green, rivers are full, and waterfalls at their most dramatic. Temperatures are mild — highs around 28–30°C, cooler at night.
The southwest monsoon (June–September) brings very heavy rainfall to the Malnad region — Agumbe, 60 km away, is one of the wettest places in India. Roads into the hills can flood or wash out and leeches are abundant on forest trails. Jog Falls is spectacular during the rains but access roads sometimes close.
March to May is hot and increasingly dry. The forests are less dramatic but bird-watching can be easier with thinner vegetation.