I read this section as outlining the effect of Weather/Darkness on travel hexes. If the Weather is Fair, and it is nighttime, you can see 10 Travel Hexes at night (15 with a full moon).
Thats ... 100 km of visibility on a clear night, 150 km with a full moon. I assume you meant to type combat hexes!
Kind of agree this belongs in combat and not travel, but it does affect non-combat encounters also.
I'm just stating what I'm interpreting from page 139. It does say "ranged combat", so I missed that, so those would be combat hexes, It really belongs in both and clarifications need to be made as to what types of hexes those numbers apply to and how those affect travel spotting distances. Also, I'm a bit bothered by the roll for weather each shift after your game starts. I'm not sure if I want to track that level of minutiae... that's great if someone is keeping a travelogue of each shift's weather, but seems like there should be some kind of weather table roll or something? Dunno.
In the end, the Weather section on page 139 needs to be re-located to the Combat section. A new Weather section should be written here in the Travel section describing how weather affects spotting distances in Travel hexes and possibly a slightly less cumbersome weather generation system.