I was in KL for the last 2 weeks. The first week was clear, then it came in over the weekend of 6/7th August. Kept getting worse and worse through the week. Worst was Thursday last week when the API (Air Pollution Index) hit about 350 in KL, and over 500 in some nearby areas. At one point I could barely see the road below from my 30th floor room at the Hilton hotel.
Lots of people wearing face masks, but according to the local media most of them were of no use against the very fine particles.
I went for dinner to Petaling Jaya on Thursday night and we originally had an outside table booked. We managed to change that for an indoor table which was the only viable option.
I avoided walking the 4 blocks from the office building to the Putra LRT station and instead used a taxi both ways.
I would not want to stay there for an extended period under those conditions. That was the worst it has been for several years. It is not uncommon at this time of year when the plantations on Sumatra go up in flames. But I would not change a planned holiday, since it can clear very quickly when they get the right winds or rain.
Singapore was clear. No issues there. In fact, the sky was clear from about 100km south of KL as was obvious from my flight on Friday from KUL to SIN.