Weather Performance Testing
Estimated Lesson Time: 35–45 Minutes
Lesson Overview
So far, you’ve learned how to benchmark different airports and aircraft while keeping your test conditions consistent.
In this lesson, we’re going to examine another major factor that influences Microsoft Flight Simulator performance:
The weather.
Weather is one of the most dynamic parts of the simulator.
It affects:
- The number of clouds the simulator must render.
- Lighting calculations.
- Visibility.
- Atmospheric effects.
- Reflections.
- Volumetric cloud rendering.
- VRAM usage.
- GPU workload.
- CPU workload.
Because weather changes constantly, it can dramatically influence benchmark results.
By the end of this lesson, you’ll understand how different weather conditions affect performance and why professional benchmarking always uses controlled weather presets.
Lesson Objectives
By the end of this lesson you will understand:
How weather affects simulator performance.
The difference between weather presets and Live Weather.
How clouds affect GPU performance.
How weather influences CPU usage.
How weather changes VRAM usage.
How to benchmark weather professionally.
Why Weather Matters
Weather is far more than visual effects.
Every cloud, shadow, rain shower and fog bank requires additional processing.
Microsoft Flight Simulator’s weather engine continuously simulates:
- Cloud volume.
- Atmospheric lighting.
- Sun position.
- Moisture.
- Visibility.
- Wind layers.
- Precipitation.
- Atmospheric scattering.
As weather becomes more complex, so does the workload placed on your PC.
1. Clear Skies
Clear Skies represents one of the lightest weather workloads.
Characteristics
- Minimal cloud rendering.
- Maximum visibility.
- Few atmospheric effects.
- Limited precipitation.
- Simple lighting.
GPU Impact
Very Low.
With very few volumetric clouds to render, the GPU spends less time processing atmospheric effects.
GPU utilisation may remain relatively low if the simulator becomes CPU limited.
CPU Impact
Low.
The weather engine performs fewer atmospheric calculations.
VRAM Usage
Lower.
Fewer cloud textures and atmospheric effects are stored in graphics memory.
Typical Result
Highest FPS.
Excellent frame pacing.
Minimal weather-related performance impact.
2. Broken Clouds
Broken Clouds introduce a much heavier workload.
The simulator now renders numerous volumetric cloud layers across the sky.
GPU Impact
Moderate to High.
The GPU must render:
- Volumetric clouds.
- Dynamic cloud shadows.
- Atmospheric lighting.
- Sunlight scattering.
Cloud rendering is one of the largest GPU workloads in Microsoft Flight Simulator.
CPU Impact
Moderate.
The simulator must update weather data and atmospheric calculations more frequently.
VRAM Usage
Higher than Clear Skies.
Additional cloud textures and atmospheric data occupy graphics memory.
Typical Result
Slight reduction in FPS.
Higher GPU utilisation.
Increased VRAM usage.
3. Storms
Storms represent one of the most demanding weather conditions available.
Heavy cloud layers combine with:
- Rain.
- Lightning.
- Dense cloud volumes.
- Low visibility.
GPU Impact
Very High.
The graphics card must process:
- Thick volumetric clouds.
- Multiple cloud layers.
- Rain effects.
- Dynamic lighting.
- Reflections from wet surfaces.
- Atmospheric scattering.
GPU utilisation often approaches maximum capacity.
CPU Impact
Moderate.
Additional weather simulation and precipitation calculations increase CPU activity.
VRAM Usage
High.
Large cloud textures, lighting data and weather effects increase memory usage.
Typical Result
Lower FPS.
Higher GPU utilisation.
More demanding frame times.
4. Rain
Rain introduces several additional rendering tasks.
The simulator now processes:
- Rain particles.
- Wet surfaces.
- Reflections.
- Reduced visibility.
- Dynamic lighting changes.
GPU Impact
High.
Rendering thousands of rain particles and wet reflections increases graphics workload.
CPU Impact
Generally lower than the GPU impact but still increased due to weather calculations.
VRAM Usage
Slightly higher than dry conditions.
Typical Result
Reduced FPS compared to clear weather.
Higher GPU utilisation.
5. Fog
Fog creates a different type of workload.
Instead of rendering large cloud formations, the simulator renders dense atmospheric scattering close to the ground.
GPU Impact
Moderate.
Fog increases atmospheric rendering but may require fewer cloud calculations than severe storms.
CPU Impact
Generally modest.
VRAM Usage
Moderate.
Typical Result
Performance varies depending on visibility distance and surrounding scenery.
6. Live Weather
Live Weather downloads real-world meteorological data and recreates current atmospheric conditions.
This includes:
- Winds.
- Clouds.
- Rain.
- Pressure.
- Temperature.
- Visibility.
Why Live Weather Is Poor for Benchmarking
No two benchmark flights will ever be identical.
Cloud positions.
Wind direction.
Visibility.
Cloud density.
Storm activity.
Everything changes.
This makes direct comparisons impossible.
Recommendation
Use Live Weather for everyday flying.
Use saved weather presets for benchmarking.
7. Weather Presets
Weather presets provide consistency.
Examples include:
- Clear Skies.
- Few Clouds.
- Broken Clouds.
- Overcast.
- Storm.
Every benchmark uses identical weather conditions.
This allows you to compare:
- Hardware upgrades.
- Driver updates.
- Graphics settings.
- Simulator updates.
Fairly.
Weather & GPU Usage
Weather primarily affects the GPU because it must render:
- Volumetric clouds.
- Atmospheric scattering.
- Dynamic lighting.
- Rain.
- Fog.
- Reflections.
- Cloud shadows.
Cloud Quality is one of the most GPU-intensive settings in Microsoft Flight Simulator.
As weather becomes more complex, GPU utilisation typically increases.
Weather & CPU Usage
Although weather mainly affects the GPU, the CPU still performs important tasks.
It processes:
- Weather simulation.
- Wind calculations.
- Atmospheric transitions.
- Environmental updates.
- Weather streaming.
The CPU impact is usually smaller than the GPU impact but becomes more noticeable in complex scenarios.
Weather & VRAM Usage
Complex weather increases VRAM usage because the GPU stores:
- Cloud textures.
- Atmospheric effects.
- Shadow maps.
- Reflection data.
- Volumetric rendering information.
Higher cloud quality settings generally require more VRAM than lower settings.
Comparing Weather
Example benchmark:
Clear Skies
Average FPS:
88
GPU Utilisation:
82%
VRAM:
8.2GB
Broken Clouds
Average FPS:
74
GPU Utilisation:
96%
VRAM:
9.6GB
Thunderstorm
Average FPS:
61
GPU Utilisation:
99%
VRAM:
10.4GB
These figures are examples only. Your results will depend on your hardware and graphics settings.
The key lesson is understanding how increasing weather complexity changes the workload on your system.
Common Mistakes
Using Live Weather for benchmarks.
Comparing different weather presets.
Ignoring cloud quality settings.
Testing at different times of day.
Assuming weather only affects FPS.
Forgetting to monitor GPU utilisation and VRAM.
Student Exercise
Today you’re going to benchmark Microsoft Flight Simulator under multiple weather conditions.
Step 1
Load your permanent benchmark flight.
Keep everything identical except the weather.
Maintain the same:
- Airport.
- Aircraft.
- Parking stand.
- Graphics settings.
- Time of day.
- Flight route.
Step 2
Run the benchmark using:
- Clear Skies.
- Broken Clouds.
- Storm or Heavy Rain preset.
If available, you may also compare with Live Weather, but do not use it as your primary benchmark.
Step 3
For each weather condition, record:
Performance
- Average FPS.
- Minimum FPS.
- 1% Lows.
- Frame pacing.
GPU
- GPU utilisation.
- VRAM usage.
- GPU temperature.
CPU
- MainThread status.
- CPU utilisation.
Notes
Record:
- Cloud density.
- Visibility.
- Smoothness.
- Any noticeable stutters.
Step 4
Compare the results.
Ask yourself:
- Which weather condition produced the highest GPU utilisation?
- How did cloud density affect FPS?
- Did VRAM usage increase with more complex weather?
- Was the simulator still CPU limited, or did the GPU become the bottleneck?
- Which weather condition best represents your normal flying?
Student Checklist
Clear Skies benchmark completed.
Broken Clouds benchmark completed.
Storm benchmark completed.
GPU utilisation recorded.
VRAM usage recorded.
CPU behaviour analysed.
Results compared.
Lesson Summary
Congratulations.
You now understand how weather influences Microsoft Flight Simulator performance.
Remember:
- Weather is one of the largest variables in benchmarking and must be controlled if you want meaningful comparisons.
- Volumetric clouds, rain and atmospheric effects primarily increase GPU workload, while the CPU continues to manage weather simulation and environmental calculations.
- More demanding weather conditions generally increase VRAM usage as additional cloud textures and rendering data are stored by the graphics card.
- Live Weather provides excellent realism for everyday flying but should be avoided when performing controlled benchmarks because conditions constantly change.
- Using consistent weather presets allows you to isolate the effect of hardware upgrades and optimisation changes with confidence.
Knowledge Check
- Why does weather have such a significant impact on Microsoft Flight Simulator performance?
- Which component is usually affected the most by complex weather conditions?
- How do volumetric clouds influence GPU workload?
- Why does VRAM usage often increase during storms?
- Why should Live Weather generally be avoided for benchmarking?
- What are the advantages of using weather presets when testing performance?
- How can weather complexity influence frame pacing as well as FPS?
- Based on your benchmark results, which weather condition placed the greatest demand on your system, and what evidence supports your conclusion?