[1] Proximity with the land, tidal and stream effects and wind variability due to geography (hills, cliffs, etc.)
This restricts gunnery, as cannon on the windward side are elevated, while the leeward gun ports aim into the sea or in heavy weather may be awash.
A ship with the weather gage, turning downwind to attack, may alter course at will to bring starboard and port guns to appropriate elevations.
Ships seeking to evade capture or attack have the advantage being downwind if they are faster vessels or are close to friendly land.
One of the last times that weather gage was perhaps a factor in a surface naval engagement was in the Battle of the Denmark Strait in 1941, where the German battleship Bismarck and the heavy cruiser Prinz Eugen held the weather gage over the British battleship HMS Prince of Wales and the battlecruiser HMS Hood.
Every time an American aircraft carrier conducted flight operations, they opened the range to the Japanese fleet.