This is an evaluation of the daily mesospheric winter temperature series derived from more than 20 years of ground-based spectral measurements of the hydroxyl airglow layer from the auroral station in Adventdalen near Longyearbyen, Svalbard (78¿N, 15¿E). The average daily OH winter temperature for the period was found to be 208¿K with a standard deviation of 15¿K. Temperature changes of 20¿K with extremes up to 40¿K within a few days are common, but some years show far less variation than others. A low December followed by a high January temperature is common but not consistent for all of the seasons. No direct relation to the solar 10.7 cm flux has been found. Mesospheric coolings are observed to be associated with stratospheric warmings. The annual mean winter temperatures show a nearly zero temperature trend, indicating no statistically significant change in the winter mesospheric temperatures over Svalbard during the last two decades.