WILL MY FLIGHT
BE DELAYED?

What causes weather delays

Weather accounts for roughly 40% of all flight delays in the US and Europe. But the mechanisms are varied — and some are far more disruptive than others.

Thunderstorms

The most disruptive weather type by far. A single convective cell over a major hub can cause cascading delays across an entire network. Thunderstorms force ground stops — periods where departures are suspended entirely — because ramp workers cannot safely operate outdoors in lightning, and aircraft cannot safely taxi through active cells. Ground stops at Chicago O'Hare or Atlanta can ripple delays across the US for hours after the storm has passed.

Low visibility and fog

Fog reduces the number of aircraft an airport can accept per hour. Most major airports are certified for instrument approaches down to CAT III conditions (visibility below 200 metres) but require specific crew qualifications and aircraft equipment. At airports without CAT III capability, even moderate fog can close the airport entirely to arriving traffic. Regional airports and smaller destinations are far more vulnerable to visibility delays than major hubs.

Snow and ice

Snow itself doesn't prevent flying — but the ground operations around it do. De-icing takes time, runways must be cleared, and aircraft need to depart within a narrow window after being de-iced before the treatment degrades. Heavy snow events typically cause average delays of 60–90 minutes even at well-prepared airports. Unexpected early-season snow, before airports have scaled up de-icing operations, tends to cause the worst disruption.

Wind

Strong crosswinds reduce the number of runway directions available and slow landing rates. Very high headwinds on approach force go-arounds. Gusts above 35–40 knots at surface level frequently cause arrival rate reductions, which back up the arrival queue and push departure delays. Airports with a single runway orientation — like London City — are particularly sensitive to crosswind direction.

The cascade effect

The least understood cause of weather delays is the one that affects the most passengers: the cascade. Your aircraft arrived late from another airport where weather was bad. The crew have reached their duty hour limit. A slot restriction at your destination was introduced three hours ago and your flight missed its window. Weather delays propagate through airline networks for 6–12 hours after the original weather event, affecting flights that never go anywhere near the original problem.

Which airports delay most

Delay rates vary dramatically by airport. Some of this is geography — airports near coastlines or in convection-prone regions face structurally more weather. Some is infrastructure — older airports with fewer runways have less flexibility. The following are consistently among the most delay-prone in the world based on BTS 2024 and Eurocontrol CODA 2024 data.

• ORD41%Chicago O'Hare. America's busiest connecting hub sits in one of its most convectively active corridors. Summer thunderstorms cause cascading network-wide disruption.
• LGW37%London Gatwick. Single runway operation with no parallel capacity. Any disruption — weather, technical, ATC — immediately queues. Fog-prone in autumn and winter.
• LIS37%Lisbon. Rapidly grown beyond infrastructure capacity. Strong Atlantic winds and slot constraints combine to create chronic delays.
• SFO30%San Francisco. Marine layer fog from the Bay suppresses visibility on a regular basis. Even in summer, morning operations are frequently impacted.
• JFK31%New York JFK. Slot-controlled airport in a congested airspace system. Weather at any New York area airport propagates instantly across all three.
• LHR32%London Heathrow. Operating at near-100% capacity with two runways. Any reduction in acceptance rate immediately creates queues measured in hours.

When delays are worst

Summer afternoons are the worst time for thunderstorm-related delays, particularly over the US and Central Europe. Convective activity peaks between 14:00 and 20:00 local time. Morning departures typically complete before convection develops.

Winter mornings carry the highest fog and snow delay risk. Dense radiation fog forms overnight and often persists through the first few hours of operation, affecting the 06:00–09:00 banking window at European hubs.

Friday evenings amplify any weather impact because aircraft and crew are at maximum utilisation across the network. A delay that would be absorbed on a Tuesday morning cascades badly on a Friday evening.

How to check your specific flight

• 01Check the day before, not weeks out. Weather forecasts beyond 3–5 days have limited skill for convective events. The most useful window for delay prediction is 12–36 hours before departure.
• 02Look at both airports, not just your destination. A delay at your origin is just as likely to affect your journey as weather at your destination — and the origin weather determines whether your inbound aircraft arrives on time.
• 03Consider your aircraft's inbound rotation. If your flight is operating as a turnaround from a delay-prone airport, the delay risk compounds. Morning first-flights of the day from base are the most reliable.
• 04Check the weathercode and CAPE, not just temperature. A warm sunny day with high CAPE (convective available potential energy) can produce severe afternoon storms with no warning in surface observations.
• 05Book morning flights when delay risk matters. First flights of the day have statistically lower delay rates — the aircraft is fresh from the overnight stand, crew are at the start of their duty window, and convection hasn't developed yet.

Frequently asked questions

Can airlines delay flights for weather that isn't that bad?

Yes, and for good reason. Airlines operate to strict safety margins and their dispatchers are working with more detailed weather data than is publicly visible. A weather delay you find frustrating at the gate may be based on forecast conditions at the destination three hours from now, not the current conditions outside the terminal.

Does travel insurance cover weather delays?

Most travel insurance policies cover delays above a threshold (typically 4–6 hours) caused by weather, though the specific conditions vary considerably between policies. Some exclude delays that were foreseeable — meaning if a major storm was forecast days in advance and you travelled anyway, the claim may be denied. Check your specific policy wording before travel.

What's the difference between a delay and a cancellation?

Airlines prefer delays over cancellations because cancellations trigger EU261 or DOT compensation obligations on top of rebooking costs. A flight that departs 5 hours late is cheaper for the airline than a cancellation even if the passenger experience is worse. Cancellations tend to be reserved for severe weather events where the delay would exceed the crew's legal duty hours, or where the weather is forecast to persist.

Is there a compensation for weather delays?

In the EU under EC 261/2004, weather is classified as an extraordinary circumstance — meaning airlines are not required to pay the standard €250–€600 compensation for weather-related delays or cancellations, though they must still provide care (meals, accommodation) for long delays. In the US, DOT rules require rebooking but do not mandate compensation for weather events. This varies by airline policy and is worth checking with your carrier directly.