OBJECTIVE: To evaluate the influence of changes in the atmospheric state on the incidence of preterm delivery (PTD) and preterm premature rupture of membrane (PPROM). STUDY DESIGN: The hospital records of PTD and/or PPROM over the year 1999 were reviewed. The current meteorological state was described by a set of parameters and their diurnal and seasonal variations. Multivariate analysis, time series approach and Poisson regression were used. RESULT: PTD occurrence was correlated with humidity and maximum temperature (P<0.01), its rise preceded their sharp variations by 3 days (P<0.01). PPROM was influenced by the variations in the weather state: desert heat wave arrival (PEuro Surveillance (Bulletin Europeen Sur Les Maladies Transmissibles; European Communicable Disease Bulletin)0.093), strong winds, overall daily differences of humidity and temperature (all with P<0.05). CONCLUSION: The rates of PTD and PPROM are affected by an ensemble of meteorological variables, specific for each disorder. Obstetricians should be aware of the influence of unstable weather on PTD and PPROM rates, especially in the spring and autumn.