How often does weather delay flights at Bâle-Mulhouse?
From January 2018 to September 2026, EUROCONTROL recorded arrival restrictions for weather (regulation reason W) at Bâle-Mulhouse (BSL) on 30 of 3,195 days (0.9%). The worst month is October: 3% of days and 0.0 minutes of weather delay per arriving flight on average. Calmest: April, September (0% of days). Weather caused 5% 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 | 1% | 0% | 0.01 |
| February | 1% | 1% | 0.02 |
| March | 1% | 0% | 0.00 |
| April | 0% | 0% | 0.00 |
| May | 1% | 0% | 0.00 |
| June | 1% | 1% | 0.06 |
| July | 1% | 1% | 0.02 |
| August | 1% | 0% | 0.01 |
| September | 0% | 0% | 0.00 |
| October | 3% | 0% | 0.02 |
| November | 1% | 0% | 0.01 |
| December | 1% | 0% | 0.01 |
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 42 (7%), week 43 (4%), week 45 (4%).
Year by year
| Year | Days with weather restrictions | Minutes per arriving flight | Arrivals |
|---|---|---|---|
| 2018 | 5 of 365 | 0.04 | 40,926 |
| 2019 | 9 of 365 | 0.02 | 42,253 |
| 2020 | 4 of 366 | 0.03 | 17,585 |
| 2021 | 4 of 365 | 0.02 | 22,146 |
| 2022 | 2 of 365 | 0.00 | 33,257 |
| 2023 | 1 of 365 | 0.01 | 35,376 |
| 2024 | 5 of 366 | 0.00 | 37,892 |
| 2025 | 0 of 365 | 0.00 | 39,965 |
| 2026 (Jan–Sep) | 0 of 273 | 0.00 | 26,449 |
2020–2021: far fewer flights during the pandemic.
Weather among all causes
| Cause of arrival regulation | Share of delay minutes |
|---|---|
| Aerodrome capacity | 30% |
| Industrial action (atc) | 22% |
| Air traffic control capacity | 20% |
| Special event | 7% |
| Weather | 5% |
| Airspace management | 5% |
| Atc staffing | 4% |
| Other | 4% |
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 | 17% | 7.1% | 2.3× |
| Fog or visibility under 800 m | 43% | 6.6% | 6.6× |
| Cloud base at or below 200 ft | 13% | 3.0% | 4.4× |
| Gusts of 30 knots or more | 30% | 5.1% | 5.9× |
| Crosswind of 20 knots or more on the best runway | 0.0% | 0.0% | — |
| Snow | 10% | 3.6% | 2.8× |
| Freezing rain or drizzle | 3.3% | 0.5% | — |
On 13% 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 |
|---|---|---|---|
| 4 June 2018 Thunderstorm reported | 790 | 121 | 6.5 |
| 11 June 2018 none of these in the airport's METAR | 643 | 160 | 4.0 |
| 11 July 2023 Thunderstorm reported; Gusts of 30 knots or more (gusts to 47 kt) | 359 | 100 | 3.6 |
| 31 August 2021 Fog or visibility under 800 m | 252 | 89 | 2.8 |
| 10 February 2020 Thunderstorm reported; Gusts of 30 knots or more (gusts to 48 kt) | 225 | 59 | 3.8 |
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 LFSB, IATA BSL. Ranking by share of restriction days: 71 of 94 airports on this site.