Fog, snow, ice and crosswinds mean that air traffic controllers have to increase the gap between planes that are landing, reducing the number of aircraft that an airport can manage. The same weather can make it slower and more difficult for the planes to taxi between runway and terminal building.

In 2026, the most common weather-related flight delays are caused by low visibility (fog), thunderstorms, and high crosswinds. Contrary to popular belief, simple rain rarely causes a delay; it is the lightning and severe turbulence associated with storms that force ground stops for ground crew safety. Dense fog is particularly disruptive because it slows down the "arrival rate" at airports, forcing larger gaps between landing aircraft, even with 2026’s advanced autoland systems. High winds can exceed the safe operating limits of certain aircraft types during takeoff or landing, especially if they are blowing perpendicular to the runway. In winter, de-icing procedures—where a glycol-based fluid is sprayed on the wings to prevent ice buildup—add significant time to departures. Even "Extreme Heat" in 2026 can cause delays, as thinner air at high temperatures reduces an airplane's lift and engine performance, occasionally requiring weight restrictions.