predawn

Predawn is the period of time immediately before sunrise. It is defined by darkness that gradually gives way to light as the sun approaches the horizon. In common usage, predawn refers to the hours before dawn, when the sky may still be dark but pale light can begin to appear along the eastern horizon. The exact boundary between predawn and dawn varies by location, season, and local convention; in some contexts predawn ends with the onset of civil dawn or astronomical dawn, while in others it is simply the interval before sunrise.

Environmental characteristics during predawn include cooler temperatures and reduced ambient light, with stars often visible in clear skies and birds and other animals beginning to stir. Wind and moisture conditions can produce dew in many regions. Geographic latitude and time of year strongly influence the duration and luminosity of predawn; high latitudes can experience lengthy predawn periods in winter, while near the equator predawn can be brief.

In everyday language, predawn is used to describe activities scheduled before daybreak, such as predawn runs or commutes, as well as in journalism, literature, and meteorology to convey quiet or preparatory phases before sunrise. In astronomy and photography, predawn light is a factor in planning observations or shoots, since sky brightness changes rapidly as dawn approaches.

See also: dawn, civil twilight, nautical twilight, astronomical twilight, sunrise.