How often does weather delay flights at London Heathrow?
From January 2018 to September 2026, EUROCONTROL recorded arrival restrictions for weather (regulation reason W) at London Heathrow (LHR) on 1,017 of 3,195 days (32%). The worst month is December: 54% of days and 3.1 minutes of weather delay per arriving flight on average. Calmest: July (14% of days). Weather caused 84% of all arrival-regulation delay minutes at this airport. Source: EUROCONTROL.
Month by month
| Month | Days with weather restrictions | Days with ≥ 1 min per arrival | Minutes per arriving flight |
|---|---|---|---|
| January | 40% | 31% | 1.54 |
| February | 45% | 37% | 2.16 |
| March | 38% | 31% | 1.69 |
| April | 24% | 19% | 1.16 |
| May | 19% | 15% | 0.85 |
| June | 18% | 14% | 0.50 |
| July | 14% | 12% | 0.46 |
| August | 21% | 16% | 0.77 |
| September | 38% | 31% | 1.61 |
| October | 40% | 32% | 1.83 |
| November | 37% | 28% | 1.64 |
| December | 54% | 46% | 3.14 |
Share of days on which EUROCONTROL's network manager limited arrivals because of weather at or around the airport (regulation reason W), 2018–2026. Minutes per arriving flight = weather-regulation delay ÷ all arrivals that month. Worst weeks of the year: week 51 (64%), week 49 (59%), week 10 (52%).
Year by year
| Year | Days with weather restrictions | Minutes per arriving flight | Arrivals |
|---|---|---|---|
| 2018 | 130 of 365 | 1.39 | 238,943 |
| 2019 | 153 of 365 | 1.55 | 239,060 |
| 2020 | 54 of 366 | 1.38 | 102,400 |
| 2021 | 8 of 365 | 0.05 | 97,663 |
| 2022 | 68 of 365 | 0.68 | 190,212 |
| 2023 | 144 of 365 | 1.46 | 228,421 |
| 2024 | 228 of 366 | 3.06 | 238,204 |
| 2025 | 150 of 365 | 1.32 | 240,069 |
| 2026 (Jan–Sep) | 82 of 273 | 0.70 | 176,646 |
2020–2021: far fewer flights during the pandemic.
Weather among all causes
| Cause of arrival regulation | Share of delay minutes |
|---|---|
| Weather | 84% |
| Air traffic control capacity | 7% |
| Aerodrome capacity | 6% |
Causes with at least 2% of all arrival-regulation delay minutes, 2018–2026.
What the weather was like on those days
| In the airport's weather reports (METAR, 05–21 UTC) | Days with weather restrictions | Other days | Ratio |
|---|---|---|---|
| Thunderstorm reported | 4.3% | 1.5% | — |
| Fog or visibility under 800 m | 7.2% | 1.0% | — |
| Cloud base at or below 200 ft | 7.1% | 1.3% | — |
| Gusts of 30 knots or more | 16% | 3.7% | 4.2× |
| Crosswind of 20 knots or more on the best runway | 2.5% | 0.2% | — |
| Snow | 1.7% | 0.9% | — |
| Freezing rain or drizzle | 0.2% | 0.0% | — |
On 69% of the restriction days none of these showed up in the airport's own reports: restrictions are also set on forecasts, for weather on the approach or elsewhere in the area, and when the wind direction forces a less efficient runway layout. The weather is what came with the delays, not proof of their cause. Based on 3,195 days with full METAR coverage.
The heaviest days
| Date and reported weather | Weather delay, minutes | Arrivals | Minutes per arrival |
|---|---|---|---|
| 27 December 2024 Cloud base at or below 200 ft | 19,801 | 643 | 30.8 |
| 27 November 2018 Fog or visibility under 800 m; Cloud base at or below 200 ft | 16,493 | 618 | 26.7 |
| 11 December 2022 Fog or visibility under 800 m; Cloud base at or below 200 ft; Snow | 16,044 | 493 | 32.5 |
| 24 November 2024 Gusts of 30 knots or more; Crosswind of 20 knots or more on the best runway (gusts to 40 kt) | 15,802 | 534 | 29.6 |
| 29 December 2024 Cloud base at or below 200 ft | 15,708 | 636 | 24.7 |
What these numbers cover
- Only delays from air traffic flow management (ATFM) regulations on arrivals are counted — not all delays, not departures, and not cancellations or diversions. A day with restrictions does not mean every flight was late.
- Airport ICAO code EGLL, IATA LHR. Ranking by share of restriction days: 2 of 94 airports on this site.