used to visit some people from sunny Jakarta who had weekend homes there
I used to live in Jakarta and often stayed in a weekend cottage on the flanks of Gunung Gede at about 3000', 13 nm east of Gunung Salak. It is hard to believe how quickly the weather can change in that area unless you have seen it.
Most mornings we would have a spectacular view of Salak with not a cloud in the sky, but by early afternoon, clouds would be developing quite quickly, with rapid changes in cloud base and distribution, particularly on the flanks of the volcanoes.
By mid- or late-afternoon, there would almost always be a severe thunderstorm. Bogor, at the foot of Salak is known as the thunderstorm capital of the world. Reputedly more than 300 storms per year.