Flew into Delhi in hopes to fly into thick smog and practice and hardcore ILS approach. Weather conditions on the METAR were reporting 0SM and my weather on my device was green. No issues there. However, on the whole approach my visibility was 50km. It seems as if it hadn’t changed from my cruise visibility. In fact, it was totally clear (50km) until my taxi off the runway when the visibility started rapidly dropping to just 1km. Is this a glitch? Was something wrong or is this normal?