Weather Basics: When to Fly or Not
You are the final decision-maker on weather. Know how temperature, pressure, wind and moisture affect both the aircraft and your judgement.
Temperature & pressure
- Temperature drops about 2 °C per 1,000 ft of altitude gained.
- Pressure drops about 1 inHg per 1,000 ft; at higher elevations the thinner air means less lift, more battery use, shorter flights.
- LiPo batteries hate extremes — cold cuts endurance, heat causes erratic power.
Wind
- Respect the manufacturer's wind limit (required by the CARs).
- Wind is usually stronger higher up than at the ground. A helpful tailwind outbound becomes a headwind on the way home — don't get caught low on battery.
- Expect gusts and rotor near shorelines, buildings and terrain. An anemometer helps you measure ground wind.
Moisture: icing, fog, thunderstorms
- Most RPA carry no de-icing — do not fly with any ice/snow on the aircraft, or into known or forecast icing.
- You are in known icing when there is visible moisture (cloud/fog) and the temperature is 0 °C or below. Ice on a propeller can cause loss of control fast.
- Fog forms when air cools to its dew point — it can drop visibility below VLOS.
Avoid flying if there is a thunderstorm within ~15 NM. Gust fronts, downbursts and microbursts produce sudden, violent wind well outside the storm's core.
Build a weather picture in the days before, then confirm on site. Use NAV CANADA aviation weather (METAR/AWOS) plus an app like Windy or WeatherCan.
Check your understanding
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Key takeaways
- ~2 °C / 1,000 ft temperature; ~1 inHg / 1,000 ft pressure; higher = less performance.
- No de-ice → no flying in/near icing; watch fog eating your VLOS.
- Thunderstorm within ~15 NM = no-go.
- Decide with current data, then trust what you see on site.
Sources: RPAS 101 pp.78–85, 43–44 · TP‑15263 §4 (Meteorology, Basic topics).