  We report on the prolonged solar-maximum conditions until late 2015 at the
north-polar region of the Sun indicated by the occurrence of high-latitude
prominence eruptions and microwave brightness temperature close to the quiet
Sun level. These two aspects of solar activity indicate that the polarity
reversal was completed by mid-2014 in the south and late 2015 in the north. .
The microwave brightness in the south-polar region has increased to a level
exceeding the level of cycle 23/24 minimum, but just started to increase in the
north. The north-south asymmetry in the polarity reversal has switched from
that in cycle 23. These observations lead us to the hypothesis that the onset
of cycle 25 in the northern hemisphere is likely to be delayed with respect to
that in the southern hemisphere. We find that the unusual condition in the
north is a direct consequence of the arrival of poleward surges of opposite
polarity from the active region belt. We also find that multiple
rush-to-the-pole episodes were indicated by the prominence eruption locations
that lined up at the boundary between opposite polarity surges. The
high-latitude prominence eruptions occurred in the boundary between the
incumbent polar flux and the insurgent flux of opposite polarity.
