The research of actual problems of safety in local emergency situations electric and magnetic fields of industrial frequency in St. Petersburg and vicinities is executed. It is established that sanitary-protective and security zones of high-voltage lines of the standard size not always provide decrease in intensity of electric fields to maximum permissible values. Dependence of intensity of electric fields of transmission lines on meteorological factors is revealed. It is established that electric fields with significant indicators of intensity are shown only near to air high-voltage lines. Working out of a technique and the organisation regular the researches, directed on monitoring and mapping of electromagnetic fields is necessary. The sizes of sanitary-protective and security zones should consider the climatic factors influencing dielectric properties of atmospheric air. Magnetic induction is not more than maximum permissible level in all cases. Magnetic fields not form sharp maxima but have practically everywhere presented city background from set of sources. Thus average indexes of a magnetic induction that above, then more intensively technogenic loading. Abnormal high values of a magnetic induction in separate points of residential areas are noted, as display of emergency situations of the technogenic character, explained by influence of electric cables of an underground lining.