Flights may be canceled due to wind, precipitation, fog or low visibility, lightning, low clouds, or storms. Outside temperature does not always affect flights. Pilots make the final determination as to whether a flight will occur or whether one in progress will be diverted to another airport.

Bad weather is the leading cause of flight delays and cancellations, affecting aviation through visibility, wind, and lightning. While modern aircraft are engineered to fly safely through heavy rain and snow, the primary issue is often "airport throughput." For example, during heavy fog or low clouds, the distance between landing aircraft must be increased to ensure safety, which reduces the number of planes that can land per hour. High "crosswinds" are particularly disruptive, as they can exceed a specific aircraft's safe landing limits, forcing a diversion to another airport. Lightning is generally not a threat to the plane itself (as the aluminum or carbon frame acts as a Faraday cage), but it is extremely dangerous for ground crews; when lightning is detected within a 5 to 10-mile radius, all baggage handling and refueling operations must stop for safety. Furthermore, winter weather requires "de-icing," a process that can add 20 to 45 minutes to a flight's departure time. Even if the weather is clear at your departure city, a storm in the flight path or at your destination can cause a "ground stop," keeping your plane at the gate until conditions improve.