Yes, thanks, I know this freeware. Really good!
But it can create a big drop in fps if you are having more layers as usual in combination with REX and a payware like the PMDG.
The most I like the weather of IVAO, but the sudden changes of the winds are annoying. When 90 knots on FL370 (realistic) changing from the left to the right in one second (not realistic) and not funny.
Back to the topic. Once I was flying to Mumbai in India and I had yellowish fog in FSX real weather. I had checked, it was smoke!