Blue Hour

The “blue hour” is not truly an hour—it typically lasts 20 to 40 minutes, depending on location, time of year, and atmospheric conditions.

It occurs just before sunrise or just after sunset, when the Sun is between 4° and 8° below the horizon, scattering shorter blue wavelengths across the sky while longer red and orange wavelengths are blocked.

The duration is shorter near the equator and longer at higher latitudes, especially during summer.

Its name reflects the distinct cool-toned ambient light, not a fixed timespan, making it more of a poetic term than a precise measurement.