This article is related to human biometeorology. It deals with the relation that has been found between the high frecuency temperature variability in the city of Vitoria (Spain), the atmosferic circulation patterns and the number of flu diagnostics that have been registered by the Basque Health Service in the 99-00 winter period in that city. According to the preliminary results, it can be established that this relation could be applied to the health services planning or, at least, they should be consired in order to avoid queuing in the emergency centers during the flu expansion period.