Resistance to acute hypoxia in rats was evaluated by the life span after elevation to an altitude of 11,500 m at 13.00-21.00 (local time) in different seasons of one year. Geomagnetic activity was evaluated using local K index for Moscow and planetary Kp index. Total 24-h geomagnetic activity had a great impact on the life span of rats. The effects of local and planetary geomagnetic activities coincided in about 70% cases. An increase in geomagnetic activity was responsible for prolongation, decrease (2-3 times more often than prolongation), and phase changes in the life span of rats, which were the most pronounced in the case of medium geomagnetic activity, during the second half of the year (in summer and particularly in autumn), in the middle and end of the day, in rats with low resistance to hypoxia.