While the weather conditions that lead to the formation of fog are usually quite benign, fog itself can be very disruptive. In particular the aviation and marine industries are often interested in how fog or mist will affect the visibility for their journeys, though fog also affects road-users.
The annual average fogs for Wellington Airport is 6 fogs per year, much rarer than at Christchurch (50 days per year) or Dunedin Airport (64 days per year) or Hamilton (92 days per year), yet it is very disruptive when it does roll in off the sea and can last for hours at a time. Interestingly, Wellington gets more fog days in summer while fogs occur in winter for many other airports. Wellington airport is a hub for domestic commercial air traffic, therefore even short closures have major flow on effects for passengers and other airports around the country.