This paper briefly reviews modern ideas about plausible mechanisms of influence of solar activity on the lower atmosphere state and weather. The possible reasons for the disturbances in the lower atmosphere are as follows: (1) variations in solar irradiance, (2) changes in the global electric circuit parameters caused by variations in cosmic ray fluxes, (3) variations in the conditions of propagation and dissipation energy of planetary waves in the atmosphere, and (4) changes in the atmospheric transparency and cloudiness are considered. Specific features of development of individual (with duration of several days) disturbances in the lower atmosphere observed during Forbush decreases of galactic cosmic rays and solar proton events are discussed. It is concluded that at latitudes of 55o--70o the disturbances considered are mainly due to variations in atmospheric transparency and cloudiness. Data on cyclic variations of the lower atmosphere state and their connection with variations in solar activity, atmospheric transparency, volcano eruptions, and other geophysical phenomena are analyzed. In conclusion, some unresolved problems of morphology of atmospheric disturbances are formulated.