Kiwi holidaymakers could be looking forward to an unusually hot and sticky January as the country is enveloped by a resurgent marine heatwave. But the elevated conditions may also worsen humidity in many places this summer, adding to uncomfortably hot days and nights. For beachgoers, a marine heatwave – defined by SSTs being at the upper bounds of historical observations for at least five days – meant noticeably balmier water.