Weather hazards for drones: wind, fog, icing and thunderstorms
Micro climate, urban wind, stability, fog and frost, icing types, thunderstorm stages and mountain turbulence for the Transport Canada drone exams.
Checked against the rules in force on 2026-10-01A small drone flies in the lowest layer of the atmosphere, where the ground shapes the weather most. The Transport Canada exams expect you to spot the hazards before they reach your site.
Micro climate and wind
Micro climate is local variation in wind, temperature, precipitation and visibility caused by terrain, water, surfaces and obstacles. Low-flying drones feel it more than any other aircraft.
Wind is reported by the direction it comes from. Around buildings, wind can double in speed, funnel between towers (a venturi effect) and swirl on rooftops. Transport Canada summarizes urban wind as speed, direction, shear, turbulence and vorticity. On the downwind side of large buildings and hills, expect gusty mechanical turbulence and sinking air.
Stable and unstable air
Cool, dry air tends to be stable: flat stratus clouds, fog, steady rain, smooth air and haze. Warm, moist air tends to be unstable: towering cumulus, showers, turbulence and usually good visibility. The standard lapse rate for unsaturated air is about 3 °C per 1,000 ft.
Fog and frost
Fog forms when air cools to its dew point. A small temperature and dew point spread is a warning. Fog can form or move in quickly, and lights on the drone do not make fog flyable if you cannot keep visual line of sight. Below freezing, moisture deposits as frost, which must be removed from propellers and other critical surfaces before takeoff.
Icing
Icing needs visible moisture and a surface at or below 0 °C. Supercooled droplets freeze on contact as rime, clear or mixed ice. Ice adds weight and destroys lift and thrust. Part IX forbids flying into known icing unless the aircraft is equipped for it.
Thunderstorms
A thunderstorm grows through the cumulus stage (updrafts), the mature stage (rain begins, every hazard at its worst) and the dissipating stage (downdrafts). Gust fronts and lightning can reach your site well ahead of the rain. Land early and secure the equipment.
Cold and the sun
Cold reduces battery capacity and your own dexterity. Strong solar activity can disturb GNSS and control links; Space Weather Canada publishes forecasts.
Sources: TC AIM RPA 3.2.22 · TP 15263 sec. 4 · FAA-H-8083-25C ch. 12
Try 5 questions on this topic
Free sample questions with a debrief for each answer.
Which conditions are typical of a stable air mass?
At dawn, the temperature is 10 °C and the dew point is 9 °C, with calm wind. What should you expect?
You plan to inspect a warehouse roof on a windy day. What hazard should you expect near the building?
You fly along a lakeshore on a sunny afternoon. Which wind should you expect?
Which conditions favour radiation fog?
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