Part 107 weather guide: what to know for the test

To handle weather questions on the Part 107 knowledge test, learn three things in order: what the rule allows, what the report says now, and what the forecast says may change. That means knowing the Part 107 visibility and cloud-clearance minimums, decoding METARs, reading TAF time groups, and connecting weather to small-drone performance.

Weather is not a side topic in the FAA blueprint. The current Remote Pilot Airman Certification Standards (FAA-S-ACS-10B) assigns 11–16 percent of the 60-question UAG test to Weather. It names METARs, TAFs, weather charts, ASOS/AWOS, and weather effects such as wind, density altitude, thunderstorms, icing, fog, ceiling, and visibility.

This guide gives you the whole map. Use the linked lessons when you want to practice one skill in depth.

PilotWrittenPrep is independent practice material. It is not an FAA website, and this guide does not replace checking current regulations and official weather before a flight.

The Part 107 weather knowledge map

The ACS divides weather into two tasks.

Sources of Weather, UA.III.A, asks whether you understand:

• internet weather briefings and flight-planning sources;
• aviation routine weather reports, or METARs;
• terminal aerodrome forecasts, or TAFs;
• weather charts; and
• automated surface and weather observing systems, ASOS and AWOS.

Effects of Weather on Performance, UA.III.B, covers:

• density altitude;
• wind and currents;
• atmospheric stability, pressure, and temperature;
• air masses and fronts;
• thunderstorms and microbursts;
• tornadoes, icing, hail, fog, ceiling, visibility, and lightning.

Basic weather minimums also appear under Airspace Operational Requirements, UA.II.B.K1. That is a useful clue about how the FAA thinks: reading a report is not the final skill. You must use the report to decide whether a flight is both legal and sensible.

You can see how weather fits beside every other test area on our Part 107 outline, or start with the broader Part 107 prep overview.

Start with the legal floor: visibility and clouds

For an operation conducted under the standard Part 107 rule, flight visibility must be at least 3 statute miles as observed from the control station. The small unmanned aircraft must also remain at least 500 feet below a cloud and 2,000 feet horizontally from a cloud. Those are the three numbers to memorize from 14 CFR § 107.51.

The numbers are only the regulatory floor. They do not promise that your aircraft can hold position in gusts, that the launch site is free of fog, or that a thunderstorm will remain far away. The remote pilot in command still has to assess the actual operating environment and aircraft limitations.

Cloud-cover codes require careful reading:

• FEW means more than zero through 2/8 of the sky covered.
• SCT means 3/8 through 4/8.
• BKN means 5/8 through 7/8.
• OVC means 8/8.
• VV reports vertical visibility into an obscuration.

For aviation purposes, the ceiling is the lowest BKN or OVC layer, or vertical visibility into a complete obscuration. FEW and SCT are not ceilings, but they are still clouds: the Part 107 distance requirement applies to the aircraft's distance from a cloud, not only to a reported ceiling.

Work through the rule and the common traps in our Part 107 cloud-clearance and weather-minimums guide.

Read the METAR for observed conditions

A METAR is a coded observation at an airport or reporting station. It tells you what was observed, not what will happen for the rest of your mission.

The FAA's current Aeronautical Information Manual, paragraph 7-1-28 and 7-1-29 presents the report in a consistent sequence:

1. report type;
2. station identifier;
3. observation date and time;
4. modifier, if needed;
5. wind;
6. visibility;
7. runway visual range, when reported;
8. weather phenomena;
9. sky condition;
10. temperature and dew point;
11. altimeter setting; and
12. remarks.

Consider this instructional example:

METAR KDEN 211753Z 17012G20KT 10SM FEW060 BKN120 30/08 A3005 RMK AO2

Read it left to right. It is a routine observation for Denver International on the 21st at 1753 UTC. Wind is from 170 degrees true at 12 knots, gusting to 20. Visibility is 10 statute miles. There are few clouds at 6,000 feet AGL and a broken ceiling at 12,000 feet AGL. Temperature is 30°C, dew point 8°C, and the altimeter setting is 30.05 inches of mercury.

For a drone mission, the attention item may be the 8-knot spread between sustained wind and gusts, even though visibility and clouds are comfortably above the Part 107 minimums. Compare both numbers with the aircraft manufacturer's limits and your own conservative operating limit.

Learn every group and decode a second example in How to read a METAR for Part 107.

Read the TAF as a timeline

A TAF is a forecast for the area around a terminal. It uses many METAR codes, but the mental task is different: you have to build a timeline.

First identify the issue time and valid period. Then split the forecast at each change group:

• FM starts a new set of prevailing conditions at a stated time.
• TEMPO describes temporary conditions expected during a stated interval.
• PROB30 indicates a 30 percent probability during its interval when used.

Do not read only the first line. A mission that begins in good conditions may extend into a lower ceiling, reduced visibility, stronger gusts, or thunderstorms in a later group. Also remember that all TAF times are UTC and can cross midnight.

A TAF is not a promise about your exact launch point. It is one forecast product for a terminal area. Terrain, shorelines, buildings, and convective cells can create important local differences. Compare the forecast with current observations and conditions at the site.

Our TAF guide for Part 107 shows how to carry conditions forward and avoid the most common time-group mistakes.

Connect reports to small-drone performance

Test questions often give you weather facts and ask for an operational consequence. Build those connections before memorizing more abbreviations.

Wind and gusts change control margin

A headwind on the outbound leg becomes a tailwind on return, and the reverse is also true. Plan battery reserve around the more demanding leg instead of assuming the displayed range is guaranteed. Gusts and mechanical turbulence near trees, roofs, ridges, and other obstacles can cause abrupt attitude changes or position errors.

Wind direction in a METAR is reported relative to true north. Do not quietly treat it as a magnetic course when a question asks you to reason about direction.

High density altitude reduces performance

Density altitude increases when air density decreases. High temperature, high field elevation, and lower pressure all push in that direction; humidity also reduces air density, though temperature and pressure are normally the larger drivers.

Less-dense air gives propellers less air to accelerate. A small UAS may need more power to produce the required thrust, reducing climb or payload margin and shortening useful battery time. The correct operational response is to consult the aircraft's performance information and reduce demands when conditions erode margin.

Stable and unstable air create different clues

Stable air tends to resist vertical motion. It is associated with smoother air, stratiform clouds, steady precipitation, haze, fog, and poorer visibility.

Unstable air supports vertical motion. Expect more turbulence, showery precipitation, cumuliform clouds, and potentially thunderstorms when enough moisture and lift are present. “Better visibility” outside precipitation does not make an unstable, convective day harmless to a drone.

Thunderstorms are a no-go hazard, not a puzzle to outsmart

Thunderstorms can bring severe turbulence, strong updrafts and downdrafts, lightning, hail, heavy precipitation, and rapidly shifting gust fronts. A microburst is a concentrated downdraft that spreads outward near the surface and can cause sharp wind changes.

The FAA Aviation Weather Handbook, FAA-H-8083-28B is the current primary reference for these hazards. For an actual operation, do not reduce the decision to whether rain has reached the launch pad. Review official products, watch the sky, and postpone when convective hazards threaten the area.

Temperature, moisture, and precipitation affect the aircraft

Cold can reduce usable battery performance. Heat can increase density altitude and place thermal stress on electronics and batteries. Rain, icing, or condensation may exceed the aircraft's environmental rating or obscure sensors. Fog and low cloud reduce the visual environment and may make both the visibility rule and safe visual line of sight impossible to maintain.

The knowledge-test answer should follow aerodynamic and regulatory principles. The real-flight decision must also follow the specific aircraft manual.

A five-step weather workflow for a Part 107 mission

Use the same sequence in practice questions and preflight planning:

1. Define the mission window and location. Include launch, route, altitude, duration, alternates, and recovery time.
2. Check the regulatory floor. Can you maintain 3 SM flight visibility and the required cloud distances throughout the planned volume?
3. Read observations. Decode the nearest useful METARs, but account for distance, terrain, and the age of each report. Observe the launch site directly.
4. Read the forecast timeline. Decode the relevant TAF and official weather products for the entire mission, not just takeoff.
5. Apply aircraft and personal limits. Compare sustained wind, gusts, temperature, precipitation, and likely changes with documented limits and a conservative reserve.

The result is not simply “legal” or “illegal.” A legal condition can still be beyond the safe capability of the aircraft, crew, or mission.

A worked Part 107 decision

Suppose the nearest METAR reports 10 SM visibility, SCT030, wind 18012G22KT, and no precipitation. The TAF forecasts FM220000 20018G28KT 4SM -TSRA BKN025CB, and your operation is expected to continue through 0030Z.

The current visibility and cloud report do not automatically prohibit the operation. The problem is the timeline: the forecast introduces stronger gusts, reduced visibility, thunderstorms with light rain, and a broken cumulonimbus ceiling during the mission window. A careful remote pilot does not use the favorable observation as permission to ignore the forecast change. Move the flight to a suitable window and verify conditions again.

On the test, look for the option that integrates all relevant facts. Distractors often focus on one comfortable number while ignoring a more serious trend or hazard.

How to study weather efficiently

Do not start by memorizing every weather contraction. Build a smaller reliable core:

• Memorize the 3 SM / 500 below / 2,000 horizontal rule.
• Decode METAR groups in their standard order until you no longer skip wind or ceiling.
• Draw a timeline for every TAF.
• Connect each hazard to a performance or decision consequence.
• Review missed questions by ACS code rather than memorizing an answer letter.

The best check is whether you can explain the answer in plain English. If you can say what was observed, what is forecast, when it changes, and why that matters to the drone, you are learning the decision process the ACS describes.

Try that process in the free demo, then use the Part 107 course to practice weather alongside airspace, regulations, loading, and operations.

Official references used

• Remote Pilot — Small UAS Airman Certification Standards, FAA-S-ACS-10B
• Aeronautical Information Manual, Chapter 7: Safety of Flight
• Aviation Weather Handbook, FAA-H-8083-28B
• 14 CFR § 107.51, Operating limitations for small unmanned aircraft

These links were checked July 21, 2026. Confirm the current version when you study or fly.