Rainbow Probability
Probability of visible rainbow formation based on solar geometry and precipitation patterns
What is Rainbow Probability?
Technical detailsRainbow Probability forecasts the likelihood of visible rainbows by analyzing solar elevation angle, precipitation patterns, cloud cover, and visibility. Rainbows require specific conditions: sunlight from behind the observer, rain or water droplets in front, and solar elevation below 42 degrees. The algorithm evaluates whether sun position, shower activity, and atmospheric clarity align for rainbow formation, distinguishing between likely vibrant rainbows and conditions where rainbows are geometrically impossible or too faint to photograph.
Templates using this field
Related rule templatesPhotography tip
How to use this conditionRainbows occur when sun is behind you and rain is in front. Best at 15-35° solar elevation during/after showers.
Rainbow Probability in photography
In depthRainbow Probability is PhotoWeather's Pro-tier metric for predicting rainbow formation, designed for photographers chasing one of nature's most iconic and challenging phenomena. Rainbows create stunning focal points in landscape photography, adding color and drama to stormy scenes, but they're notoriously difficult to predict because they require precise alignment of solar geometry, precipitation, and atmospheric conditions. Many photographers miss rainbows because standard weather forecasts don't account for the physics of rainbow formation.
PhotoWeather's algorithm addresses this by modeling the specific requirements: solar elevation must be below 42 degrees (the critical angle for rainbow refraction), which means rainbows can only occur when the sun is relatively low—typically within 2-3 hours of sunrise or sunset. Higher sun angles make rainbows geometrically impossible to see from the ground. The sun must be behind the observer while rain or water droplets are in front, creating the antisolar geometry needed for light refraction and reflection. The algorithm analyzes precipitation patterns to identify showery conditions (isolated rain showers rather than widespread overcast rain), which favor rainbow formation because they provide rain droplets with clear sky and sunlight nearby. Cloud cover is critical—the antisolar sky where the rainbow appears must be relatively clear (low cloud cover allows the rainbow to be visible), while the solar side needs breaks in clouds for sunlight to penetrate. Visibility matters for rainbow brightness: clear air with good visibility produces vibrant, saturated rainbows, while haze and reduced visibility create faint, washed-out rainbows. The algorithm also considers rain intensity: moderate rain produces the best rainbows, while light drizzle yields faint arcs and heavy rain obscures visibility.
Scores above 70% indicate favorable conditions where solar angle, showery precipitation, and atmospheric clarity align for rainbow photography. Photographers typically set thresholds of 60-70% and combine this condition with time-of-day filters to catch rainbows during optimal light windows. This derived field is essential for rainbow photography, helping photographers position themselves with the sun at their backs and anticipate when those magical arcs will appear.
Frequently asked questions
Common questionsWhat is Rainbow Probability?
Rainbow Probability forecasts the likelihood of visible rainbows by analyzing solar elevation angle, precipitation patterns, cloud cover, and visibility. Rainbows require specific conditions: sunlight from behind the observer, rain or water droplets in front, and solar elevation below 42 degrees. The algorithm evaluates whether sun position, shower activity, and atmospheric clarity align for rainbow formation, distinguishing between likely vibrant rainbows and conditions where rainbows are geometrically impossible or too faint to photograph.
How does Rainbow Probability affect photography?
Rainbows occur when sun is behind you and rain is in front. Best at 15-35° solar elevation during/after showers.
What values are typical for Rainbow Probability?
Rainbow Probability typically ranges from 0% to 100%. PhotoWeather monitors these values to help you identify ideal conditions for your photography goals.
How is Rainbow Probability calculated?
Rainbow Probability is an advanced derived condition calculated from multiple weather parameters including Solar Elevation, Total Precipitation, Rainfall, Showers, Total Cloud Coverage. 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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Combines aurora activity with viewing conditions (darkness, cloud cover, visibility) to provide photography-ready aurora quality scores. Aurora activity is OVATION-aware from the compute step.
Blue Hour Quality
Evaluates atmospheric conditions for blue hour photography quality. Scores sky clarity, cloud type suitability (high thin clouds ideal), visibility, and calm conditions.
Fiery Red Sky Potential
Atmospheric suitability for fiery red sky conditions across extended time window around sunrise/sunset periods. Enhanced with CAMS aerosol data (AOD, particle composition, Ångström exponent) and GFS upper-air humidity for improved color prediction.
Fog Probability
Multi-factor fog formation likelihood combining visibility, dewpoint spread, humidity, and time-of-day analysis
Golden Hour Potential
Atmospheric suitability for golden hour photography across extended time window around golden hour periods
Golden Clouds Potential
Cloud formation suitability for golden hour photography across extended time window around golden hour periods
Cloud Drama Score
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
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
Comprehensive atmospheric clarity analysis for landscape and astrophotography using CAMS aerosol optical depth, particle composition (dust, smoke, sea salt), particle size distribution (Ångström exponent), and visibility conditions.
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.
Solar Elevation
Sun's angle above horizon (0° = horizon, 90° = zenith)
Total Precipitation
Combined rain and snow precipitation
Rainfall
Liquid precipitation amount
Showers
Shower-type precipitation (brief, heavy bursts)
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