Find the next event
The page calculates the next sunrise or sunset for Assateague National Seashore.
Great color usually needs three things: a clear path for warm light, clouds in the right place to catch it, and enough clean air for that light to reach you.
The short version
Forecast in. Sky outlook out.
Read the atmosphere
It checks cloud layers, humidity, visibility, and the weather near the horizon.
Estimate color potential
Those conditions become a 0 to 100 score and a plain-language outlook.
Why the sky glows
The light takes the long way home.
Near sunrise and sunset, sunlight travels through more atmosphere than it does at midday. More blue light gets scattered away, which leaves warmer reds, oranges, and yellows to reach your eyes.
A clear horizon helps
Warm light needs an open path from below the horizon. A thick cloud bank in that direction can shut down the show.
Some clouds are good
Middle and high clouds can act like a canvas, catching warm light before sunrise and after sunset.
Low clouds can block it
Low, thick clouds often sit between you and the light. They can turn a colorful setup into a flat grey one.
Clearer air keeps color alive
Heavy haze and moisture can mute contrast. Better visibility gives the light a cleaner path through the lower atmosphere.
Inside the number
What goes into the score
The score is a weighted recipe. It rewards an open horizon, enough cloud to catch the light, fewer low clouds, and clearer lower air.
Open light path near the horizon40%
The biggest factor. Distant cloud in the sunrise or sunset direction can block the warm light before it reaches the scene.
Middle and high clouds to catch color32%
The model likes a moderate amount, not a totally clear sky and not a solid overcast.
Low clouds staying out of the way18%
Fewer low clouds means less chance of the view being blocked close to the horizon.
Visibility and lower humidity10%
These are simple clues about how clear the lower atmosphere may be.
A score of 100 is not a 100 percent chance. It only means the forecast closely matches this model's favorite setup.
Looking down the light path
It checks more than the weather overhead.
For sunset, the model looks west. For sunrise, it looks east. It samples cloud forecasts near Assateague and at three distant points along the direction of the sun, each paired with the cloud layer the light actually passes through there: low cloud at the nearest, middle cloud next, and high cloud at the farthest.
These are forecast sample points, not visibility distances.
Why look that far away? The useful color window often begins before sunrise and continues after sunset, while the sun is near or below the horizon. Clouds farther along that light path can decide whether warm light reaches the clouds above you.
The moving background
The forecast is real. The artwork is an interpretation.
Live mode
Uses current conditions when available, then blends in hourly forecast data for cloud cover and weather.
Moving through the day
Use the timeline to preview the next 24 hours. Drag the handle or tap a sunrise or sunset marker, then choose Live to return to now. It uses forecast conditions for the selected future time and is not a historical replay.
Sun and twilight
The sun's position is calculated for Assateague. Night colors follow civil, nautical, and astronomical twilight. Suggested arrival and stay times mark the useful civil twilight window, not an exact prediction of when the strongest color will appear.
Moon and stars
Moonrise, moonset, and phase use astronomical calculations. The stars are a simplified visual layer.
Keeping it honest
What the outlook can miss
Sunrise and sunset color is wonderfully sensitive. Small forecast errors can make a big visual difference.
Fast-changing clouds
A narrow break can open or close after the latest model update.
Cloud thickness
Cloud cover does not perfectly describe whether a layer is thin, glowing, or completely opaque.
Smoke, dust, and sea haze
The model only uses humidity and visibility as simple clues. It does not directly measure every particle in the air.
Local surprises
Fog banks, small showers, horizon obstructions, and shifting weather can all change the view.
This is not a beach safety forecast
The color score does not evaluate park or beach access, tides, surf, lightning, wind risk, driving conditions, or closures. Check official park and weather information before heading out.
Sources and further reading
Where the data and science come from
Live forecast data comes from the National Weather Service and Open-Meteo. Forecast requests refresh and cache for about 10 minutes, so visitors share one recent result instead of each device calling the services separately. Cloud layers come from a single named model, ECMWF, rather than an automatic blend, so the outlook stays consistent from one hour to the next instead of jumping as different models take over. Open-Meteo data is used under CC BY 4.0. OSV Count combines and transforms the forecast data into its original experimental color score and visual interpretation.
National Weather Service APISky cover, visibility, and relative humidity forecast data
Open-Meteo forecast APICloud layers, precipitation, and weather codes
Astronomy EngineMoon position, phase, moonrise, and moonset calculations
NASA light scattering explainerWhy low-angle sunlight turns warm near sunrise and sunset
National Weather Service cloud guideHow high, middle, and low clouds differ
NOAA red sky scienceHow air molecules and aerosols shape sky color