Part 107 Weather Theory
Updated October 27, 2026
The Part 107 weather section tests two things: reading weather reports (see how to read METARs and TAFs) and understanding how weather affects a small drone. Here are the theory topics that come up most, followed by free practice questions.
Density altitude
Density altitude is the altitude the air “feels like” to the aircraft. High, hot and humid conditions mean thinner air, so density altitude rises and performance drops: propellers make less lift, so the drone climbs more slowly and its flight time can shorten.
Stability
| Stable air | Unstable air |
|---|---|
| Smooth air | Turbulence |
| Stratus (layered) clouds | Cumulus (heaped) clouds |
| Poor visibility, haze and fog | Good visibility, except in showers |
| Steady precipitation | Showery precipitation |
Thunderstorms
A thunderstorm needs moisture, rising (unstable) air and a lifting force. It goes through three stages: cumulus (updrafts), mature (rain starts falling and updrafts and downdrafts are strongest) and dissipating (mostly downdrafts). Stay well away: outflow winds and gusts can reach far beyond the storm.
Fog
- Radiation fog: forms on clear, calm nights as the ground cools, often in low areas.
- Advection fog: forms when moist air moves over a colder surface, common along coasts.
- Fog is most likely when the temperature and dew point are close together.
Fronts and wind
- A cold front often brings a sudden wind shift, gusty winds and thunderstorms, followed by clearer, cooler air.
- A warm front brings gradual lowering clouds, steady precipitation and reduced visibility.
- Wind flowing over buildings, trees and hills creates turbulence on the downwind side. Near the ground, expect gusts and eddies around obstacles.
Free weather practice questions
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How does high density altitude affect a small drone?Answer: BHigh density altitude means thinner air, so the propellers produce less lift. The drone climbs more slowly and works harder.
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Which conditions cause the highest density altitude?Answer: DHigh, hot and humid conditions all make the air less dense, which raises density altitude.
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Which is typical of stable air?Answer: AStable air resists vertical movement, giving layered stratus clouds, smooth air and often haze or fog.
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In which stage of a thunderstorm are updrafts and downdrafts strongest, with rain falling?Answer: BThe mature stage begins when precipitation starts falling and has the strongest updrafts and downdrafts.
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Fog is most likely to form when:Answer: CWhen the temperature and dew point are close, the air is near saturation, and fog or low clouds can form.
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Where is turbulence most likely when wind blows across a large building?Answer: AWind flowing over and around obstacles creates eddies and turbulence on their downwind (leeward) side.
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When the temperature and dew point are close together, what is likely?Answer: CA small temperature–dew point spread means the air is near saturation, so fog, mist or low clouds are likely.
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In the Northern Hemisphere, air circulates around a high-pressure area:Answer: DIn the Northern Hemisphere, winds flow clockwise and outward around high pressure, and counterclockwise and inward around low pressure.
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What is a temperature inversion?Answer: ANormally temperature falls with altitude. In an inversion it rises, which traps haze and smoke and can produce smooth air with poor visibility below.
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Which weather phenomenon is especially dangerous to small drones because of strong, sudden downdrafts?Answer: BMicrobursts are intense, localized downdrafts that spread out near the ground, with sudden wind shifts that can easily overpower a small drone.
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What is required for a thunderstorm to form?Answer: CThunderstorms need enough water vapor, an unstable lapse rate and something to lift the air, such as heating or a front.
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What happens to air density as temperature increases?Answer: DWarmer air is less dense, which raises density altitude and reduces a drone's performance.
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A cold front passing through usually brings:Answer: ACold fronts often cause a sudden wind shift, falling temperatures and showery, sometimes stormy weather along the front.
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Which type of fog forms when moist air moves over a colder surface?Answer: BAdvection fog forms when moist air moves over a cooler surface, often along coasts. Radiation fog forms on clear, calm nights as the ground cools.
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Mountain wave turbulence is most likely when:Answer: CStrong winds crossing a ridge at right angles in stable air can create waves and severe turbulence on the downwind side.
Pass the FAA Part 107 drone test on your first try
- All 308 questions across regulations, airspace, weather, loading and operations
- An explanation for every answer, with the rule or FAA source behind it
- Questions on the real test's figures: the FAA's sectional charts, METARs, TAFs and load factor chart, zoomable on any screen