Short answer: the wind speed in a forecast is an average over several minutes; a gust is a short peak inside it, measured over about 3 seconds. Your drone has to survive the peaks, not the average, so compare the gust figure with its wind rating. A forecast of 20 km/h with gusts of 36 km/h is a 36 km/h day for a DJI Mini 4 Pro (rated 38 km/h), not a 20 km/h one.
What the two numbers mean
Wind speed (mean wind). Weather services smooth out the turbulence of the air by averaging. The WMO guide works with 10-minute averages, "as used for forecasting purposes", at the standard height of 10 m above the ground.
Gust. A brief burst above that average, measured in two common ways:
- The 3-second peak. The Met Office defines gust speed as "the maximum three-second average wind speed within a given period", and the WMO says a gust duration of about 3 s "accommodates most potential users". The peak gust is the highest value in the period, for example the last hour.
- The 10-knot rule. The FAA's Aviation Weather Handbook defines gusts as rapid fluctuations "with a variation of 10 kt or more between peaks and lulls", the same threshold as the US National Weather Service glossary. An airport report of a west wind at 20 kt gusting 35 kt reads 27020G35KT. Since 10 kt is about 18.5 km/h, smaller variations are not reported as gusts at all.
When you read an hourly forecast, check what the gust covers. Open-Meteo, the default source of Drone Weather Forecast, gives gusts at 10 m "as a maximum of the preceding hour": the 14:00 value is the strongest gust between 13:00 and 14:00.
Why the wind gusts
The FAA handbook lists the causes of turbulence, and they are what makes the wind gusty near the ground:
- Obstacles. Trees, buildings and hills break the wind into "a complex snarl of eddies"; "the higher the speed and/or the rougher the surface, the greater the turbulence." A field beside a tree line is gustier than an open beach in the same wind.
- Sunshine. Convective currents "are most active on warm summer afternoons when winds are light", and dry thermals give "little or no indication of their presence".
- Storms. A thunderstorm's gust front brings a "rapid and sometimes drastic change in surface wind" and can run "up to 15 mi" ahead of the rain. A storm in the distance is already a reason to land.
The gust factor
The WMO calls the ratio of the maximum gust to the mean wind over the same period the gust factor: it measures how bumpy the wind is, whatever its strength. The example forecasts below are judged against a DJI Mini 4 Pro (38 km/h) with the app's thresholds: green up to 90 % of the limit (34.2 km/h), yellow up to the limit, red above.
| Wind | Gusts | Gust factor | Gusts vs 38 km/h | Mini 4 Pro hour |
|---|---|---|---|---|
| 15 km/h | 22 km/h | 1.5 | 58 % | green |
| 30 km/h | 36 km/h | 1.2 | 95 % | yellow |
| 20 km/h | 36 km/h | 1.8 | 95 % | yellow |
| 22 km/h | 44 km/h | 2.0 | 116 % | red |
The last row is the trap: a 22 km/h average is only 58 % of the limit, but the gusts are above it.
Worked example: DJI Mini 4 Pro
DJI rates the Mini 4 Pro for 10.7 m/s (38 km/h) of wind. Its top speed is 12 m/s in Normal and Cine mode, 16 m/s in Sport.
You plan a flight over a town park. The 14:00 forecast says wind 19 km/h, gusts 37 km/h:
- Wind: 19 km/h is 50 % of the limit. Green.
- Gusts: 37 km/h is 97 % of the limit. Yellow, and this is the number that counts. The gust factor is almost 2.
- Margin: 37 km/h is about 10.3 m/s. Flying home into that gust in Normal mode leaves roughly 12 − 10.3 = 1.7 m/s (6 km/h) of ground speed. Rough arithmetic, but it shows how slow the return can get.
- Height: the forecast is for 10 m; at 100–120 m the wind is usually stronger (wind at altitude).
- Timing: with Open-Meteo, 37 km/h is the strongest gust of the hour before 14:00, so do not count on a lull.
Decision: pick a calmer hour, or stay low, close and fly upwind first so the way home has the wind behind you. For other drones, look up the rating (how much wind a drone can handle) or try your numbers in the drone wind calculator.
How Drone Weather Forecast checks it
Choose your drone from 79 presets or type its limits (default 38 km/h). For every hour the app compares both the wind and the gusts with that limit: green up to 90 %, yellow up to the limit, red above. A calm average cannot hide strong gusts, because the gusts are checked on their own. The Pro wind profile shows wind and estimated gusts at 10, 80, 120, 180 m and higher. Data comes from Open-Meteo by default, with Apple WeatherKit and WeatherAPI as options.
Sources
- WMO Guide to Instruments and Methods of Observation, chapter 5: surface wind (10-minute averages, peak gust, 3 s gust duration, gust factor)
- Met Office: what is wind and how do we measure it? (gust speed definition)
- National Weather Service glossary: gust
- FAA Aviation Weather Handbook, FAA-H-8083-28B (METAR gust coding; chapter 19, turbulence and gust fronts)
- Open-Meteo API documentation (wind_gusts_10m)
- DJI Mini 4 Pro specifications (wind resistance, maximum speeds)
More guides
- Can you fly a drone in the rain?
- Flying a drone in cold weather
- The KP index explained for drone pilots
- How many satellites does a drone need?
- Wind at altitude: why it is windier up there
- Drone pre-flight checklist
- UAV Forecast alternatives in 2026
- How much wind can a drone handle?
- Can you fly a drone in fog?
- Flying a drone in hot weather
- Drone wind calculator
- Wind speed converter and Beaufort scale