To determine whether meteorologic conditions affect the respiratory status of individuals with chronic lung disease, we asked 14 patients who had completed outpatient pulmonary rehabilitation to record the following information daily during the spring and summer of 1991: (1) dyspnea on arising (morning dyspnea); (2) dyspnea throughout the day (daytime dyspnea); (3) peak expiratory flow rate (PEFR); (4) mood; and (5) the presence of lower respiratory tract infection (LRI). The effect of local meteorologic conditions and LRI frequency on morning and daytime dyspnea, PEFR, and mood were analyzed for spring and summer seasons using a linear regression technique that controlled for first-order autocorrelation. The LRI frequency and the preceding day's respiratory status were the most significant predictors of either season's daily variation in respiratory status. During spring, the only meteorologic condition associated with respiratory status was precipitation: rainfall was directly related to increased morning and daytime dyspnea. Meteorologic conditions were not related to changes in PEFR or mood. During summer, the combination of higher temperature, rise in barometric pressure, and increased LRI frequency best predicted increased morning dyspnea, while the combination of higher temperature and rise in barometric pressure best predicted reduced PEFR. Meteorologic conditions were not related to changes in daytime dyspnea or mood. Precipitation in spring and a combination of high temperature and rise in barometric pressure in summer best predicted deterioration in the respiratory status of this group of patients with chronic lung disease.