It’s my understanding that I should be able to clearly see an object that is as distant as the reported visibility.
KMDW with the visibility defaulting to 10sm, Willis Tower is 9.5sm distant:
KONT with visibility reported at 0.25sm. The KONT tower is 0.25sm distant:
It seems like they’ve set this so that pretty much all visibility is gone at the reported distance, and that’s excessive. Expected VFR flights based on METAR reports can become IFR as a result. For example, an approach into KONT the other day with METAR reporting 8sm, and I couldn’t make out the runway at 2sm, which is below the legal minimums for VFR flight at that location.