Primary: BMKG
public forecast. Live METAR/SIGMET: NOAA AWC;
hourly model & VMC/IMC: Open-Meteo.
Official aviation portal: BMKG Aviation.

VMC/IMC rules: any rain, thunderstorm/lightning, fog, visibility < 5 km,
low cloud ≥ 85% or rain probability ≥ 60% → IMC. Disclaimer: public
information, not an official aviation weather product. Obtain current METAR/TAF/SIGMET/NOTAM
from BMKG and AirNav Indonesia before flight.