We report from a continuuous 24-hour measurement of the OH (8--3) band emission in the nightglow at 78.4¿N. A mean temperature of 273 K and a mean band intensity of 596 R were observed. Extreme temperature variations were seen with amplitudes up to ¿70 K from the mean. It is suggested that these variations are related to the passage of internal gravity waves. If so, the extreme amplitudes of the variations might imply that the OH emitting layer is situated above 90 km at this latitude in January. The deduced &ngr; values (ΔI/I/ΔT/T) favor the ozone mechanism to be responsible for the OH emission with the possibility of an additional mechanism contributing up to 5%.