The magnetic field of the Earth is influenced by the electromagnetic environment of the solar system. The disturbed interplanetary environment changes the conditions of the natural electromagnetic environment of our planet and affects normal operation of space and ground technological infrastructures, such as power grids and pipelines. The geomagnetically induced currents that directly affect vulnerable infrastructure are driven by the geoelectric (telluric) field. Therefore, the most important task in space weather hazard mapping is to identify the areas with different levels of telluric activity. On the map, telluric activity is defined as the annual percentage of the time when variations in the activity is above the normal level of 20 milliVolts per kilometre. Elevated telluric activity occurrs for a quarter of the year in the auroral zone, whereas it varies from 15 percent (4.5 times per month) down to just a few percent (1 occurrence per two months) in the Prairies. It is interesting to note that most of the big cities in Canada, and therefore much of the infrastructure, are in the least tellurically active zone (less than 10 percent).