Scientists are puzzling over whether it has rained more than once at the North Pole.

Researchers on an ice-breaker near the Pole were stunned when it started raining in September last year, around the time the Arctic summer ice shrank to the smallest on record.

It was the first rain recorded at the top of the world — leading scientists to wonder if it was a one-off downpour, perhaps a sign of global warming, or maybe something that happens every now and then as part of the normal Arctic weather.

“We are trying to find out,” David Carlson, director of the International Polar Year – a current research effort by hundreds of scientists – told Reuters.

“But it’s not that easy a question — who operates a rain gauge at the North Pole?” he asked, noting that any gauges would freeze and be useless.

He reckoned that it had “probably” rained before German scientist Ursula Schauer wrote of a day of rain in a Sept. 11 blog from aboard the Polarstern research vessel (pictured above) 150 km (95 miles) from the North Pole.

After reading her blog, “several of us said: ‘where would you go to find out whether that has ever happened before’?” Carlson said.

Carlson reckoned that the best chances of finding out whether it rained probably lay in Moscow’s archives about research camps set up on the ice drifting on the Arctic Ocean, some of them near the Pole. Aviation records for planes landing and taking off at the makeshift ice airstrips would probably say whether it was raining at the time.

Maybe Arctic explorers should pack an umbrella in future?