Drillhole-determined sea-ice thickness was compared with values derived remotely using a portable small- offset loop-loop steady state electromagnetic (EM) in- duction device during expeditions to Fram Strait and the Siberian Arctic, under typical winter and summer con- ditions. Simple empirical transformation equations are derived to convert measured apparent conductivity into ice thickness. Despite the extreme seasonal differences in sea-ice properties as revealed by ice core analysis, the transformation equations vary little for winter and sum- mer. Thus, the EM induction technique operated on the ice surface in the horizontal dipole mode yields accu- rate results within 5 to 10% of the drillhole determined thickness over level ice in both seasons. The robustness of the induction method with respect to seasonal extremes is attributed to the low salinity of brine or meltwater filling the extensive pore space in summer. Thus, the average bulk ice conductivity for sum- mer multiyear sea ice derived according to Archie's law amounts to 23 mS/m compared to 3 mS/m for winter conditions. These mean conductivities cause only minor differences in the EM response, as is shown by means of 1-D modeling. However, under summer conditions the range of ice conductivities is wider. Along with the widespread oc- currence of surface melt ponds and freshwater lenses underneath the ice, this causes greater scatter in the ap- parent conductivity/ice thickness relation. This can result in higher deviations between EM-derived and drillhole determined thicknesses in summer than in winter.