<p>Predicting the strength and peak time of geomagnetic activity for the ensuing cycle 25 is important in space weather service for planning future space missions. The minimum <i>aa</i> geomagnetic index around the solar minimum has been often used to predict the maximum amplitude of sunspot cycle, but seldom used to directly predict the maximum <i>aa</i> index. This study analyzed the relationships between the maxima and minima of both the geomagnetic <i>aa</i> and <i>Ap</i> indices for the 11-year cycle. The maximum <i>aa</i> index is found to be well correlated to the preceding minimum with a correlation coefficient of <i>r</i> = 0.860. As a result, the maximum <i>aa</i> index for the ensuing cycle 25 is predicted to be <i>aa</i><sub>max</sub>(25) = 26.9 ± 2.6. This value is equivalent to <i>Ap</i><sub>max</sub>(25) = 17.3 ± 1.8 ± 1.2 if employing the high correlation between <i>aa</i> and <i>Ap</i> (<i>r</i> = 0.939).</p> <p>The maximum <i>Ap</i> index is also found to be well correlated to the preceding minimum with a correlation coefficient of <i>r</i> = 0.862. Based on this correlation, the maximum <i>Ap</i> index is predicted to be a slightly higher value of <i>Ap</i><sub>max</sub>(25) = 19.0 ± 1.6. The rise time of the <i>aa</i> (<i>Ap</i>) index for the 11-year cycle is found to be nearly uncorrelated to the following maximum, <i>r</i> = −0.16 (−0.17). If the data point for cycle 24 (which is far from others) were not considered, the rise time of the <i>Ap</i> index for the 11-year cycle would be weakly correlated to the following maximum, <i>r</i> = −0.404 at a confidence level of 62 %. The rise time for cycle 25 would be roughly estimated to be 89.9 ± 31.6 (months), implying that the geomagnetic activity for the ensuing cycle 25 would peak around April 2025 ± 32 months.</p>