Indonesia has a variable climate, with mostly tropical weather. The humidity of the Island is quite high, with always a high level of humidity. The areas can have extreme levels of rainfall during the months form September to November. Indonesia has frequent tropical storms (like monsoons) because of the wet climate and high temperature. The monsoonal seasons are there because the Island goes through dry and wet times during the year.

Typhoons which hit the Islands can cause extreme winds and heavy rainfall. The western and Northern parts of Indonesia experience the most rainfall since the monsoons are very heavy with moisture by the time they reach these areas.

Although, Indonesia experiences these rapid changes in climate and weather, but typhoons are not always devasting, sometimes they are only on a small scale and few in between. The only recommendations that can really be made is wear proper clothing and keep umbrellas for sudden outbursts of rainfall.

http://thejakartaglobe.beritasatu.com/archive/super-extreme-weather-is-the-worst-on-record/

http://www.weatheronline.co.uk/reports/climate/Indonesia.htm