Fog Probability
Multi-factor fog formation likelihood combining visibility, dewpoint spread, humidity, and time-of-day analysis
What is Fog Probability?
Technical detailsFog Probability predicts the likelihood of fog formation by analyzing the convergence of multiple meteorological factors. The algorithm evaluates visibility (fog's defining characteristic), dewpoint spread (temperature-dewpoint gap indicating saturation), relative humidity, vapor pressure deficit, wind conditions, and precipitation patterns. Light winds and high humidity create ideal fog conditions, while strong winds and precipitation typically prevent or dissipate fog.
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Related rule templatesPhotography tip
How to use this conditionValues above 70% indicate excellent fog conditions for atmospheric photography.
Fog Probability in photography
In depthFog Probability is PhotoWeather's comprehensive fog forecast designed specifically for atmospheric and landscape photographers who seek misty, ethereal conditions. Fog creates unique photographic opportunities—soft diffused light, simplified compositions with reduced backgrounds, mysterious moody atmospheres, and the chance to capture light beams, halos, and glowing subjects. However, fog is notoriously difficult to predict because it requires precise meteorological conditions to form and persist.
PhotoWeather's algorithm combines multiple factors to assess fog likelihood: visibility is the primary indicator (values below 5km suggest fog, below 1km confirms dense fog), dewpoint spread measures how close the air is to saturation (spreads under 2°C strongly favor fog), relative humidity above 90% indicates air nearly saturated with moisture, and vapor pressure deficit quantifies the atmosphere's moisture demand. Wind plays a dual role—light winds (2-5 km/h) mix the surface layer to encourage fog formation, but strong winds prevent fog by disrupting the stable layer needed for moisture condensation. The algorithm also considers precipitation: recent light rain can saturate the air and cool the ground, setting up fog conditions, whereas heavy rain or snow typically prevents fog through mixing.
Time-of-day patterns matter too—radiation fog forms overnight and peaks around dawn as temperatures reach their minimum, making early morning the prime window for fog photography. Scores above 80% indicate excellent fog conditions with visibility, humidity, and wind all aligned. Photographers typically set thresholds of 70-80% to catch developing fog situations while filtering out marginal chances. This derived field is essential for photographers planning shoots around fog, mist, or low cloud, providing actionable forecasts that account for the complete atmospheric state rather than relying on single variables like humidity alone.
Frequently asked questions
Common questionsWhat is Fog Probability?
Fog Probability predicts the likelihood of fog formation by analyzing the convergence of multiple meteorological factors. The algorithm evaluates visibility (fog's defining characteristic), dewpoint spread (temperature-dewpoint gap indicating saturation), relative humidity, vapor pressure deficit, wind conditions, and precipitation patterns. Light winds and high humidity create ideal fog conditions, while strong winds and precipitation typically prevent or dissipate fog.
How does Fog Probability affect photography?
Values above 70% indicate excellent fog conditions for atmospheric photography.
What values are typical for Fog Probability?
Fog Probability typically ranges from 0.0% to 100.0%. PhotoWeather monitors these values to help you identify ideal conditions for your photography goals.
How is Fog Probability calculated?
Fog Probability is an advanced derived condition calculated from multiple weather parameters including Visibility, Temperature, Dew Point, Relative Humidity, Vapor Pressure Deficit. PhotoWeather's algorithms analyze these factors to provide a single, easy-to-understand score for this photography opportunity.
Typical values
Value rangeRelated fields
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Analysis of cloud formations and atmospheric conditions for dramatic sky photography
Storm Intensity
Storm intensity analysis combining precipitation, wind conditions, atmospheric pressure, visibility, GFS simulated radar reflectivity, and wind shear for enhanced storm organization detection.
Frost Probability
Frost formation probability combining temperature, dewpoint spread, cloud cover, and wind analysis
Rainbow Probability
Probability of visible rainbow formation based on solar geometry and precipitation patterns
Coastal Drama Score
Analysis of coastal conditions combining wave dynamics, atmospheric conditions, and lighting for dramatic seascape photography. Evaluates wave height, swell patterns, spray potential, and atmospheric drama factors.
Atmospheric Clarity Score
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Light Breakthrough Potential
Likelihood of sun breaking through clouds creating dramatic rays and dappled light patterns. Best with partial cloud cover (40-70%) and some sunshine reaching the surface.
Soft Light Index
Quality of diffused light for portrait and product photography. High scores indicate soft, even lighting that minimizes harsh shadows - the 'giant softbox' effect.
Cloud Texture Score
Rates how visually interesting the clouds are - distinguishing dramatic formations from boring flat overcast. High scores indicate structured clouds with good light transmission.
Overcast Flatness
How flat and boring the overcast is. HIGH scores indicate uniform gray sky with no breaks or texture - generally unfavorable for most photography. LOW scores indicate breaks, texture, or clearing.
Dewpoint Spread
Temperature difference between air temperature and dew point
Visibility
Horizontal visibility distance
Relative Humidity
Moisture content relative to saturation
Wind Speed
Wind speed at 10 meters above ground
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